Clin Genet 2011: 80: 550–557Printed in Singapore. All rights reserved

© 2010 John Wiley & Sons A/SCLINICAL GENETICS

doi: 10.1111/j.1399-0004.2010.01595.x

Short Report

Clinical and molecular characterizationof Diastrophic Dysplasia in the Portuguesepopulation

Barbosa M, Sousa AB, Medeira A, Lourenco T, Saraiva J, Pinto-Basto J,Soares G, Fortuna AM, Superti-Furga A, Mittaz L, Reis-Lima M,Bonafe L. Clinical and molecular characterization of Diastrophic Dysplasiain the Portuguese population.Clin Genet 2011: 80: 550–557. © John Wiley & Sons A/S, 2010

SLC26A2 -related dysplasias encompass a spectrum of diseases: from lethalachondrogenesis type 1B (ACG1B; MIM #600972) and atelosteogenesistype 2 (AO2; MIM #256050) to classical diastrophic dysplasia (cDTD;MIM #222600) and recessive multiple epiphyseal dysplasia (rMED; MIM#226900). This study aimed at characterizing clinically, radiologically andmolecularly 14 patients affected by non-lethal SLC26A2 -related dysplasiasand at evaluating genotype–phenotype correlation. Phenotypically, eightpatients were classified as cDTD, four patients as rMED and two patientshad an intermediate phenotype (mild DTD – mDTD, previously ‘DTDvariant’). The Arg279Trp mutation was present in all patients, either inhomozygosity (resulting in rMED) or in compound heterozygosity with theknown severe alleles Arg178Ter or Asn425Asp (resulting in DTD) or withthe mutation c.727-1G>C (causing mDTD). The ‘Finnish mutation’,c.-26+2T>C, and the p.Cys653Ser, both frequent mutations innon-Portuguese populations, were not identified in any of the patients ofour cohort and are probably very rare in the Portuguese population. Atargeted mutation analysis for p.Arg279Trp and p.Arg178Ter in thePortuguese population allows the identification of approximately 90% ofthe pathogenic alleles.

Conflict of interest

All the authors declare not having conflicts of interest.

M Barbosaa,b, AB Sousac,A Medeirac, T Lourencod,J Saraivae, J Pinto-Bastof,G Soaresa, AM Fortunaa,A Superti-Furgag, L Mittazg,M Reis-Limah and L Bonafeg

aUnidade de Genetica Medica, Centro deGenetica Medica Dr. Jacinto Magalhaes,Instituto Nacional de Saude Dr. RicardoJorge, Porto, bInstituto de Investigacaoem Ciencias da Vida e da Saude, Escolade Ciencias da Saude, Universidade doMinho, Braga, cServico de GeneticaMedica, Hospital de Santa Maria, Lisboa,dServico de Genetica Medica, Hospitalde Dona Estefania, Lisboa, eServico deGenetica Medica, Hospital Pediatrico deCoimbra, Coimbra, fCentro de GeneticaPreditiva e Preventiva, Instituto deBiologia Molecular e Celular, Porto,Portugal, gDivision of MolecularPediatrics, Centre Hospitalier UniversitaireVaudois, Lausanne, Switzerland, andhUnidade de Genetica Medica, HospitalPrivado da Boavista, Porto, Portugal

Key words: diastrophic dysplasia –genotype – phenotype correlation –recessive multiple epiphyseal dysplasia– SLC26A2 – sulfate transporter

Corresponding author: MafaldaBarbosa, Unidade de Genetica Medica,Centro de Genetica Medica Dr. JacintoMagalhaes, Praca Pedro Nunes,88, Porto 4099-028, Portugal.Tel.: +351 226 070 300;fax: +351 226 070 399;e-mail:mafalda.barbosa@insa.min-saude.pt

Received 30 August 2010, revised andaccepted for publication 8 November2010

550

Clinical and molecular characterization of DTD

SLC26A2 -related chondrodysplasias are a groupof skeletal disorders because of recessive muta-tions in the ‘diastrophic dysplasia’ (DTD) sulfatetransporter (DTDST). DTD(MIM #222600) is themost known phenotype of the SLC26A2 muta-tion spectrum, which spans from lethal achondro-genesis type 1B (ACG1B; MIM #600972) andatelosteogenesis type 2 (AO2; MIM #256050)to classical DTD (cDTD) and recessive multi-ple epiphyseal dysplasia (rMED; MIM #226900).No reliable data exist regarding the frequency ofSLC26A2 -related chondrodysplasias, but these dis-orders are generally believed to occur in approxi-mately 1:100,000 (1).

Clinically, DTD is characterized by short-limbeddwarfism, normal-sized skull, cleft palate, cysticear swelling, small chest, protuberant abdomen,spinal deformities, large joint contractures, radiusdislocation, hitchhiker thumbs and clubfeet (2, 3).Radiographic findings include cervical kyphosis,bell-shaped chest, hypoplastic ilia with flat acetab-ula, shortened long bones with metaphyseal flaring,flat epiphyses, kyphoscoliosis with caudal reduc-tion of interpeduncular distance, bowed radiusand tibia brachydactyly, hitchhiker thumb, ulnardeviation of the fingers, shortness of the firstmetacarpal, delta-shaped proximal and middle pha-langes (2, 3).

rMED is characterized by childhood-onset jointpain at hips and knees, mild brachydactyly,mildly shortened or normal stature and congenitalclubfoot in some cases (4).

The SLC26A2 gene (MIM #606718, locus 5q32-q33.1) consists of a 5′ untranslated exon with reg-ulatory functions and two coding exons. SLC26A2encodes a sulfate transporter that belongs to thefamily of anion exchangers known as solute car-rier family 26 (SLC26) (5). The sulfate/chlorideantiporter is predicted to have 12 transmem-brane domains and a carboxy-terminal, cytoplas-mic, moderately hydrophobic domain. This trans-porter is crucial for the uptake of inorganic sulfateinto chondrocytes in order to maintain adequatelevels of intracellular sulfate and allowing propersulfation of the proteoglycans (6, 7). The SLC26A2gene is expressed not only in developing carti-lage in human fetuses but also in a wide varietyof other tissues (5, 7). Phenotypic manifestationsof DTDST mutations are not restricted to skeletonbut involve other organs containing cartilage tissue(e.g. external ears and larynx) and the ligamentousapparatus (e.g tendons and joint capsules).

Impaired activity of the sulfate transporter inchondrocytes and fibroblasts causes intracellularsulfate depletion, which leads to insufficientlysulfated proteoglycans (8, 9). Hence, cartilage

has reduced total sulfate content and containsundersulfated glycosaminoglycans (9–11), whichcompromise enchondral bone formation (7, 12).

Recent studies in transgenic mice showed thatproteoglycans are not only structural componentsof cartilage architecture, but also play a dynamicrole in the regulation of chondrocyte growth anddifferentiation (13).

The four most common SCL26A2 mutationsare p.Arg279Trp, c.-26+2T>C (also known as‘Finnish allele’), p.Arg178Ter and p.Cys653Ser.These mutations account for 70% of disease alle-les (66% in DTD cases and 90% in rMED cases)and can be detected by restriction enzyme diges-tion and gel electrophoresis screening. Sequenceanalysis may detect rarer mutations (1, 14).

The predicted severity of the mutations canbe correlated with the residual activities ofthe sulfate transporter and the severity of thephenotypes (10–12, 14–17). In humans, corre-lations between SLC26A2 mutations and clin-ical phenotypes have been described: ‘severe’mutations (premature truncation of the proteinor mutations in transmembrane domains) leadto the absence/minimal residual activity of thesulfate transporter and homozygosity or com-pound heterozygosity results in a severe phenotype(ACG1B) (18). ‘Mild’ mutations (missense muta-tion in non-transmembrane domain, cytoplasmictail of the protein or in the regulatory 5′-flankingregion) produce a protein with significant residualactivity, which leads to either rMED (‘mild’ muta-tion in homozygosity) or to a mild form of DTD(in association with a ‘severe’/‘moderate’ muta-tion). Hence, dealing with a recessive disorder, themilder mutation tends to ‘rescue’ the effect of asevere mutation (14, 19).

In the current literature, all reports of largeseries of patients with DTD are from Finland,where most patients present homozygosity for the‘Finnish mutation’. However, these conclusionsmay not apply to other populations. This studyaimed at recruiting a cohort of DTD/rMED patientsfrom Portugal and at studying their clinical andmolecular aspects.

Patients and methods

Patients

The four main Portuguese Services of MedicalGenetics and four Orthopedics Services were con-tacted in order to recruit, at a national level,patients already diagnosed as DTD or rMED orsuspected of being affected by these disorders.We invited the physicians in those services to

551

Barbosa et al.

fill in a screening protocol that we designed witha list of signs and symptoms compatible withSLC26A2 -related, non-lethal, skeletal dysplasias(limb shortening, normal-sized skull, trunk short-ening, hitchhiker thumbs, small chest, protuberantabdomen, contractures of large joints, dislocationof the radius, cleft palate, cystic ear swelling inthe neonatal period, ulnar deviation of the fingers,gap between the first and second toes, clubfootand flat hemangiomas of the forehead). Fourteenpatients were selected for detailed clinical exami-nation and X-ray review. All patients were referredby the Medical Genetics Services; eight of themwere already in follow-up in the Orthopedics Ser-vices (and six patients were not being followed inOrthopedics).

A clinical protocol concerning family and per-sonal history and tailored physical exam was per-formed in all patients. Heights were plotted againstcharts developed from Finnish DTD patients (20).Skeletal survey was requested and analyzed in allof them.

The clinical protocol, the photos and the X-rayswere reviewed by the authors with the largestexperience on these disorders (ASF and LB), whoconfirmed the diagnosis. Thereafter, the selectedpatients were screened for SLC26A2 (DTDST)mutations. All patients with the clinical diagnosismade by us were mutation positive.

Molecular analysis

The SLC26A2 gene was amplified by polymerasechain reaction (PCR) and screened for the fourmost common mutations by restriction enzymedigestion and gel electrophoresis. Subsequently,selective fragments of the gene were analyzedby bi-directional fluorescent direct sequencing.Results were confirmed in a second amplificationproduct. If both mutations were not identified, theentire gene was then amplified by PCR and ana-lyzed by bi-directional fluorescent direct sequenc-ing. Mutations have been classified according toGenBank accession number U14528. Nucleotide1 has been counted as the first nucleotide ofthe sequence, with nucleotide 28 being the firstnucleotide of the translation initiation codon.

Results

Clinical characterization

The clinical data of the patients can be consultedin Table 1. Fourteen patients were recruited, ninemales and five females, with ages varying between2 and 40 years (17 years on average). Phenotyp-ically, eight patients were classified as cDTD,

four patients as rMED and two patients presentedwith an intermediate phenotype between DTD andrMED (mild DTD, mDTD). All patients were cau-casian and from ancient Portuguese descent. Nohistory of consanguinity was reported in any ofthe patients.

In order to accurately evaluate the growth of thepatients, their height was plotted against graphicsdesigned specifically for DTD patients (20). How-ever, these graphics have been designed based ona population of Finnish patients most of whom arehomozygous for the ‘Finnish’ mutation, which ismild. Moreover, the average height of the back-ground Portuguese population is lower than thatof northern Europeans. Patients with cDTD in ourseries were indeed under the 25th centile (some ofthem even under the 10th centile). Patients withmDTD were around the 25th centile and patientswith rMED were above the 50th centile.

Concerning the craniofacial abnormalities, facialdysmorphism (high forehead, forehead heman-gioma, downslanting and short palpebral fissures,long nose with hypoplastic alae nasi and smallmouth) was only detected in cDTD. Patients withboth cDTD and mDTD consistently presented dys-plastic ears and hoarse voice (possible because ofchanges in the laryngeal cartilage structures). Cleftpalate was more common in cDTD (37.5% of thepatients) but, interestingly, one patient (P13) of therMED group presented bifid uvula.

All patients with DTD presented spine defor-mities, the most common being cervical kyphosis.Arthrosis of the hips was a common complaint inpatients older than 25 years.

Limb shortening, bowed diaphyses and contrac-tures of large joints were present in all patientswith DTD, while only occasionally in patients withrMED. The typical hand findings were striking incDTD but subtle in the mDTD. Clubfeet and short-ened Achilles tendons were present in almost allpatients (DTD and rMED). However, the youngestand also least affected patient of this cohort onlypresented limitation of dorsiflexion of the feet.

Most patients underwent orthopedic surgery.However, despite multiple surgeries of the feet, theoutcome was poor in most of them. Two patientshad surgery for spinal cord decompression becauseof severe kyphoscoliosis. It has been recentlyshown that early surgical intervention might be abetter option in many patients with DTD as bracetreatment does not prevent progression of spinaldeformities (21). Concerning quality of life, allpatients had limitations; the degree of autonomycould not be predicted by their genotype. Infact, different outcomes were observed in patientswith the same genotype. Possible explanations

552

Clinical and molecular characterization of DTDTa

ble

1.C

linic

al,r

adio

logi

cala

ndm

olec

ular

char

acte

rizat

ion

ofth

e14

patie

nts

Pat

ient

12

34

56

78

910

1112

1314

Gen

der

FF

MM

MM

FM

MF

MM

MF

Age

(yea

rs)

1512

2437

4026

366

1212

67

82

Fam

ilyhi

stor

yS

Ac

TOP

TOP

—S

A(6

)S

A(5

)—

——

——

—S

A(1

4)S

A(1

3)H

eigh

t(ce

ntile

)a<

1010

<10

<10

<10

25<

1010

–25

2525

9075

50–7

550

–75

Cra

niof

acia

lD

ysm

orph

ism

++

++

−—

—+

——

——

——

Cle

ftpa

late

—+

+—

——

+—

——

——

+—

Dea

fnes

s+

+—

——

——

——

+—

——

—D

yspl

astic

ear

++

++

++

++

++

——

——

Hoa

rse

voic

e+

++

—+

++

++

+—

+—

—S

pine Cer

vica

lkyp

hosi

sb+

++

++

++

—+

+—

——

—Lu

mba

rlo

rdos

isb

+—

—+

——

++

—+

++

——

Sco

liosi

sb+

+—

++

—+

——

+—

——

—A

rthr

osis

ofhi

p—

——

++

++

——

+—

——

—Li

mb

shor

teni

ngb

++

++

++

++

++

++

+B

owed

diap

hisi

sb+

++

++

++

++

++

——

—C

ontr

actu

res

++

++

++

++

++

——

+—

Han

dsB

rach

ydac

tyly

b+

++

++

++

++

+—

—+

+H

itchh

iker

thum

bsb

++

++

++

++

——

——

——

Fing

ers:

ulna

rde

viat

ionb

++

++

++

++

++

++

+P

hala

ngea

lsyn

osto

sisb

++

++

++

++

+—

——

——

Pre

tibia

ldim

ples

+—

+—

——

+—

+—

——

——

Feet C

lubf

ootb

++

++

++

++

++

++

+—

Sho

rten

edte

ndon

s+

++

++

++

++

++

—+

—Tr

eatm

ents

Phy

siot

hera

py+

++

++

++

++

++

++

—S

urge

ry:c

lubf

oot/

tend

on+

++

++

++

++

++

++

—S

urge

ryof

spin

e+

——

——

—+

——

——

——

—O

utco

me

PP

PA

PA

AA

PA

GG

PG

Phe

noty

pecD

TDcD

TDcD

TDcD

TDcD

TDcD

TDcD

TDcD

TDm

DTD

mD

TDrM

ED

rME

DrM

ED

rME

DM

olec

ular

anal

ysis

ofR

279W

R27

9WR

279W

R27

9WR

279W

R27

9WR

279W

R27

9WR

279W

R27

9WR

279W

R27

9WR

279W

R27

9WS

LC26

A2

gene

R17

8XR

178X

R17

8XR

178X

R17

8XR

178X

N42

5DR

178X

c.72

7-1G

>C

c.72

7-1G

>C

R27

9WR

279W

R27

9WR

279W

A,a

ccep

tabl

e(a

uton

omou

sam

bula

tion)

;cD

TD,c

lass

ical

dias

trop

hic

dysp

lasi

a;F,

fem

ale;

G,g

ood

(aut

onom

ous

inev

eryd

aylif

eac

tiviti

es);

M,m

ale;

mD

TD,m

ilddi

astr

ophi

cdy

spla

sia;

P,p

oor(

noam

bula

tion)

;rM

ED

,rec

essi

vem

ultip

leep

iphy

seal

dysp

lasi

a;S

A,s

ibaf

fect

ed(in

brac

kets

isth

eat

trib

uted

num

bero

fthe

sibl

ing

inou

rcoh

ort);

TOP

,ter

min

atio

nof

preg

nanc

yof

affe

cted

fetu

s;N

425D

=A

sn42

5Asp

;R17

8X=

Arg

178T

er;R

279W

=A

rg27

9Trp

.aA

ccor

ding

toth

egr

owth

curv

espr

opos

edby

Mak

itie

etal

.(20

).bFe

atur

esbe

tter

appr

ecia

ted

inth

eX-

Ray

s.cS

ib-a

ffect

edde

ceas

edin

neon

atal

perio

d.

553

Barbosa et al.

Fig. 1. Radiological features. Patients with classical diastrophic dysplasia (cDTD) present kyphoscoliosis, upper and lower limbshow shortened long bones with some metaphyseal flaring, bowed radius and tibia, hands with hitchhiker thumb with ulnar deviationof the fingers, hypoplastic ilia with flat acetabula and clubfeet. Patients with mild diastrophic dysplasia (mDTD) present similarbut milder radiological presentation than cDTD. Patients with recessive multiple epiphyseal dysplasia show moderately shortenedlong bones, hypoplastic ilia with flat acetabula and club feet.

could subside in the genetic background, medicalmanagement, treatment options/timing/availabilityand family support.

Concerning the X-Ray analysis (Fig. 1, Table 1),we verified that all patients with cDTD presentedwith skull of normal size, cervical kyphosis, short-ened long bones with some metaphyseal flaring,bowed radius and tibia, abnormalities of the hands(with hitchhiker thumb with ulnar deviation of thefingers being the most striking) and hypoplasticilia with flat acetabula. mDTD patients had similarbut milder radiological presentation. Patients withrMED consistently presented with skull of normal,moderately shortened long bones, hypoplastic withflat acetabula ilia and club feet.

Molecular characterization

Molecular characterization of the patients is pre-sented in Table 1. Four known mutations wereidentified in our patients: c.559C>T (p.Arg178Ter), c.727-1G>C (previously described as g.IVS2-1G>C), c.862C>T (p.Arg279Trp) and c.1300A>G (p.Asn425Asp) (Fig. 2).

Discussion

This paper reports the largest series of DTDpatients in a non-Finnish population. All patients

had short stature; however, the severity wasdecreasing from cDTD to mDTD and to rMED.Patients with DTD (both classical and mild) con-sistently presented dysplastic ear and hoarse voice,cervical kyphosis, limb shortening, bowed dia-physis, contractures of the large joints, clubfeetand shortened Achilles tendons. Hand findingswere more severe in cDTD than in mDTD andhitchhiker thumbs were only identified in cDTD.Patients with rMED commonly had clubfeet andsubtle hand finding (moderate brachydactyly withulnar deviation of the second finger).

Although specific features can be attributed tothe different phenotypes, it is interesting to notethat there is also an overlap between the differentphenotypes. This is shown here between DTD andrMED (Fig. 3), but it is also true for the otherSLC26A6 -related dysplasias (between ACG1Band AO2 and between AO2 and DTD) (22–26).The spectrum of SLC26A2 -related dysplasias canhence be described as a continuum, while also con-tinuously expanding (27). Apart from the combi-nation of different mutations in the SLC26A2 gene,the variations in phenotypes could be due to mod-ifiers of the SLC26A2 gene, to variations of othergenes involved in sulfate metabolism (6, 7, 13), aswell as to the genetic background and environ-ment. The significant role of these factors can be

554

Clinical and molecular characterization of DTD

Fig. 2. The sulfate transporter encoded by the SCL26A2 gene is represented as a horizontal bar; the 12 putative transmembranedomains are shaded dark gray and the cytoplasmic domains are shaded light gray. The mutations identified in our patients areshown: Arg178Ter – diamond; c.727-1G>C – arrow; Arg279Trp – circle; and Asn425Asp – triangle.

best appreciated in the two pairs of siblings ofthe cohort (patients 5 and 6 and patients 13 and14) with slightly different presentation and signif-icantly different outcome while carrying the samemutations. The older pair of sibs (patients 5 and6), presenting with cDTD, have overlapping phe-notypes except for the presence of scoliosis andsevere clubfeet in the eldest brother that has lim-ited his ambulation. Both brothers were surgicallyinterventioned multiple times (five times the eldestand seven times the youngest). The other pair ofsibs, affected with rMED, had more significantlydifferent phenotypes: besides a bifid uvula, theelder brother had contracture of knees and clubfeetthat, together, restrained his ambulation. On thecontrary, his sister was very mildly affected andthe diagnosis could be suspected only by familyhistory and careful physical exam.

Four known mutations were identified in ourpatients: c.559C>T (p.Arg178Ter), c.727-1G>C,c.862C>T (p.Arg279Trp) and c.1300A>G (p.Asn425Asp). The mutations p.Arg178Ter and p.Asn425Asp are localized in transmembrane domains(Fig. 1) and hence are predicted to cause a severe

disruption of the sulfate transporter function.Mutation p.Arg178 Ter is a recurrent mutation thatresults in ACG1B when homozygosity or com-pounded with another severe mutation. Indeed,functional studies have showed that sulfate trans-porters bearing the p.Arg178X and p.Asn425Aspmutations have residual activity of <10% com-pared to the wild-type transporter (28). The mis-sense mutation p.Arg279Trp occurs in an extracel-lular loop. Indeed, functional analysis showed thatthe DTDST transporters bearing that mutation had39–62% activity compared to the wild type (16).The c.727-1G>C, very rare in non-Portuguesepopulations, is thought to interfere with the splic-ing and has been described as pathogenic (29). Thepresence of this mutation in 2 of 14 unrelated Por-tuguese patients may indicate that this variant ismore common in the Portuguese population.

As previously reported, Arg279Trp, which is a‘mild’ mutation (with significant sulfate transporterfunction) in homozygosity, causes the phenotypeof rMED, but the association of this ‘mild’mutation with a null mutation (Arg178Ter) or amissense mutation in the transmembrane domain

Fig. 3. Clinical spectrum of SLC26A2 patients.

555

Barbosa et al.

(Asn425Asp) (both leading to the absence ofST function) cause the intermediate phenotype ofDTD.

Our experience on molecular testing forSLC26A2 (DTDST) mutations in 350 non-Finnishnon-Portuguese Caucasian chromosomes showthat four common mutations (p.Arg279Trp, p.Arg178X, p.Cys653Ser and IVS1+2T>C or ‘Finnish’mutation) account for about 70% of all pathogenicalleles (30, 31), with p.Arg279Trp being present inabout 44% of alleles and the other three mutationsrepresenting each about 9% of all pathogenic alle-les. Although the patients presented here representonly a sample (28 chromosomes) of Portuguesepatients with SLC26A2 -related dysplasias, it isnoteworthy that p.Arg279Trp accounted for 64%and p.Arg178Ter for 25%. Thus, a targeted muta-tion analysis for p.Arg279Trp and p.Arg178Terin the Portuguese population would be expectedto identify approximately 90% of the pathogenicalleles.

Acknowledgements

We are grateful to our patients and their families for their generouscollaboration. This work was supported by the Swiss NationalResearch Foundation (grant number 320000-116506) to L. B.,Division of Molecular Pediatrics, Lausanne, Switzerland.

References

1. Bonafe L, Superti-Furga A. Diastrophic dysplasia. GeneRe-views at gene tests: medical genetics information resource(database online). Seattle, WA: University of Washington,2007: 1993–2004. Accessed 2010, from http://www.genetests.org.

2. Superti-Furga A. Defects in sulfate metabolism and skeletaldysplasias. In: Scriver CR, Beaudet AL, Sly WS, Valle D,Vogelstein B, Childs B, eds. The metabolic and molecularbases of inherited disease, 8th edn. McGraw-Hill, New York,2001: 5189–5201.

3. Superti-Furga A. Skeletal dysplasias related to defects in sul-fate metabolism. In: Royce P, Steinmann B, eds. Connectivetissue and its heritable disorders, 2nd edn. Wiley-Liss Inc, NewYork, 2002: 939–960.

4. Ballhausen D, Bonafe L, Terhal P et al. Recessive multipleepiphyseal dysplasia (rMED): phenotype delineation in eigh-teen homozygotes for DTDST mutation R279W. J Med Genet2003: 40: 65–71.

5. Mount DB, Romero MF. The SLC26 gene family of mul-tifunctional anion exchangers. Pflugers Arch 2004: 447:710–721.

6. Pecora F, Gualeni B, Forlino A et al. In vivo contribution ofamino acid sulfur to cartilage proteoglycan sulfation. BiochemJ 2006: 398 (3): 509–514.

7. Forlino A, Piazza R, Tiveron C et al. A diastrophic dysplasiasulfate transporter (SLC26A2) mutant mouse: morphologicaland biochemical characterization of the resulting chondrodys-plasia phenotype. Hum Mol Genet 2005: 14 (6): 859–871.

8. Satoh H, Susaki M, Shukunami C, Iyama K, Negoro T,Hiraki Y. Functional analysis of diastrophic dysplasia sul-fate transporter. Its involvement in growth regulation of

chondrocytes mediated by sulfated proteoglycans. J Biol Chem1998: 273: 12307–12315.

9. Rossi A, Kaitila I, Wilcox WR et al. Proteoglycan sulfationin cartilage and cell cultures from patients with sulfatetransporter chondrodysplasias: relationship to clinical severityand indications on the role of intracellular sulfate production.Matrix Biol 1998: 17: 361–369.

10. Rossi A, Bonaventure J, Delezoide AL, Cetta G, Superti-Furga A. Undersulfation of proteoglycans synthesized bychondrocytes from a patient with achondrogenesis type1B homozygous for an L483P substitution in the dias-trophic dysplasia sulfate transporter. J Biol Chem 1996: 271:18456–18464.

11. Rossi A, Bonaventure J, Delezoide AL, Superti-Furga A,Cetta G. Undersulfation of cartilage proteoglycans ex vivo andincreased contribution of amino acid sulfur to sulfation in vitroin McAlister dysplasia/atelosteogenesis type 2. Eur J Biochem1997: 248: 741–747.

12. Corsi A, Riminucci M, Fisher LW, Bianco P. Achondrogene-sis type IB: agenesis of cartilage interterritorial matrix as thelink between gene defect and pathological skeletal phenotype.Arch Pathol Lab Med 2001: 125: 1375–1378.

13. Cornaglia AI, Casasco A, Casasco M, Riva F, Necchi V.Dysplastic histogenesis of cartilage growth plate by alterationof sulphation pathway: a transgenic model. Connect TissueRes 2009: 50 (4): 232–242.

14. Rossi A, Superti-Furga A. Mutations in the diastrophic dyspla-sia sulfate transporter (DTDST) gene (SLC26A2): 22 novelmutations, mutation review, associated skeletal phenotypes,and diagnostic relevance. Hum Mutat 2001: 17: 159–171.

15. Rossi A, Cetta G, Piazza R, Bonaventure J, Steinmann B,Supereti-Furga A. In vitro proteoglycan sulfation derivedfrom sulfhydryl compounds in sulfate transporter chondrodys-plasias. Pediatr Pathol Mol Med 2003: 22: 311–321.

16. Karniski LP. Functional expression and cellular distribution ofdiastrophic dysplasia sulfate transporter (DTDST) gene muta-tions in HEK cells. Hum Mol Genet 2004: 13: 2165–2171.

17. Maeda K, Miyamoto Y, Sawai H et al. A compound het-erozygote harboring novel and recurrent DTDST mutationswith intermediate phenotype between atelosteogenesis type IIand diastrophic dysplasia. Am J Med Genet A 2006: 140:1143–1147.

18. Superti-Furga A, Hastbacka J, Wilcox WR et al. Achondroge-nesis type IB is caused by mutations in the diastrophic dyspla-sia sulphate transporter gene. Nat Genet 1996: 12: 100–102.

19. Bonafe L, Mittaz-Crettol L, Ballhausen D, Superti-Furga A.Multiple epiphyseal dysplasia, recessive. GeneReviews atgenetests: medical genetics information resource (databaseonline). Seattle, WA: University of Washington, 2010:1993–2010. Accessed 2010, from http://www.genetests.org.

20. Makitie O, Kaitila I. Growth in diastrophic dysplasia. J Pediatr1997: 130 (4): 641–646.

21. Jalanko T, Remes V, Peltonen J, Poussa M. Helenius I. Treat-ment of spinal deformities in patients with diastrophic dys-plasia: a long-term, population based, retrospective outcomestudy. Spine 2009: 34 (20): 2151–2157.

22. Maeda K, Miyamoto Y, Sawai H et al. A compound heterozy-gote harboring novel and recurrent DTDST mutations withintermediate phenotype between atelosteogenesis type II anddiastrophic dysplasia. Am J Med Genet A 2006: 140 (11):1143–1147.

23. Megarbane A, Haddad FA, Haddad-Zebouni S et al. Homozy-gosity for a novel DTDST mutation in a child with a ‘broadbone-platyspondylic’ variant of diastrophic dysplasia. ClinGenet 1999: 56 (1): 71–76.

556

Clinical and molecular characterization of DTD

24. Bieganski T, Faflik J, Kozlowski K. Diastrophic dysplasiawith severe primary kyphosis and ‘monkey wrench’ appear-ance of the femora. Australas Radiol 2000: 44 (4): 450–453.

25. Panzer KM, Lachman R, Modaff P, Pauli RM. A phenotypeintermediate between Desbuquois dysplasia and diastrophicdysplasia secondary to mutations in DTDST. Am J Med GenetA 2008: 146A (22): 2920–2924.

26. Miyake A, Nishimura G, Futami T et al. A compound het-erozygote of novel and recurrent DTDST mutations results in anovel intermediate phenotype of Desbuquois dysplasia, dias-trophic dysplasia, and recessive form of multiple epiphysealdysplasia. J Hum Genet 2008: 53 (8): 764–768.

27. Bonafe L, Hastbacka J, de la Chapelle A et al. A novelmutation in the sulfate transporter gene SLC26A2 (DTDST)specific to the Finnish population causes de la Chapelledysplasia. J Med Genet 2008: 45 (12): 827–831.

28. Karniski LP. Mutations in the diastrophic dysplasia sul-fate transporter (DTDST) gene: correlation between sulfate

transport activity and chondrodysplasia phenotype. Hum MolGenet 2001: 10 (14): 1485–1490.

29. Hastbacka J, de la Chapelle A, Mahtani MM et al. Thediastrophic dysplasia gene encodes a novel sulfate transporter:positional cloning by fine-structure linkage disequilibriummapping. Cell 1994: 78 (6): 1073–1087.

30. Bonafe L, Mittaz Crettol L, Ballhausen D, Superti-Furga A.Achondrogenesis type 1B. GeneReviews at genetests: medicalgenetics information resource (database online). Seattle, WA:University of Washington, 2009: 1993–2002. Accessed 2010,from http://www.genetests.org.

31. Bonafe L, Mittaz Crettol L, Ballhausen D, Superti-Furga A.Atelosteogenesis type 2. GeneReviews at genetests: medicalgenetics information resource (database online). Seattle, WA:University of Washington, 2009: 1993–2002. Accessed 2010,from http://www.genetests.org.

557