Tracing Neuronal Cell Development and Maturation

in the Mouse Spinal Cord

Kelly Probst

Dr. Michael Gross Laboratory

Sensory Information

Somatosensory

Visual

Auditory

Olfactory

Gustatory

Vestibular

ExteroceptiveTouch, Temperature, Pain

Proprioceptive Body Position

InteroceptiveStatus of Viscera

Somatosensory Information

Sensory Information Flow

BrainSpinal Cord

Body

Visceral Afferents

AA

Dorsal Root Ganglion(DRG))

Spinal Cord

Spinal Cord Innervation by Sensory Neurons

Spinal Relay Interneurons

Thalamus

Hindbrain

Cerebellum

Sensory Neuron

Relay Interneuron

Synaptic Connection

Ventricular Zone

Mantle Zone

SMG1

G2

PMG0

Neurons Born (E10.5 to E13.5)

Early Embryonic Interneuron Populations

VZ

MZ

Isl1-2 = I3

Foxd3 = I2

Lbx1 = I4

Project Objective• Match adult ascending tracts with embryonic

neural tube populations

• Identify when in development these relay axonal projections reach the brain

?

Backfill Analysis

Flour-Dextran

Contralateral

Ipsilateral

Embryo Dissection

Hindbrain

C1 (Atlas)

Cervical Vertebrae

Fill

TMR-dextran Fill

Filled Neuron

Incubation

Spinal Cord/Brain Dissection

Fill Site

Brachial Enlargeme

nt

Cervical Region

Abdominal Region Lumbar Region and

Enlargement

Hindbrain-Spinal Cord Junction

E18.5 Backfilled Spinal Cord

1 cm

Section 27(27 sections X 100 m = 2.7 mm)

Dorsal

Ventral

E17.5 Backfilled Spinal Cord

1 cm

Section 10(10 sections X 100 m = 1.0 mm)

Dorsal

Ventral

E16.5 Backfilled Lbx1 +/- Spinal Cord

1 cm

Section 28(28 sections X 40 m = 1.1 mm)

Dorsal

Ventral

Conclusions

• By embryonic day 16.5, the axons of some relay interneurons have reached the hindbrain

• A subset of these relay interneurons express Lbx1 and therefore are derived from the I4, I5, or I6 embryonic populations

Future Goals

• Backfill younger spinal cords

• Backfill from specific brain regions

• Co-label backfills with more marker combinations

Acknowledgements

Dr. Michael Gross

Dr. Kevin Ahern

Howard Hughes Medical Institute