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
Somatosensory Information
Exteroceptive
Touch, Temperature, Pain
Proprioceptive
Body Position
Interoceptive
Status of Viscera
Sensory Information Flow
Visceral Afferents
Brain
Spinal
Cord
Body
Spinal Cord Innervation by Sensory Neurons
Dorsal Root Ganglion
(DRG))
A
A
Spinal Cord
Spinal Relay Interneurons
Thalamus
Hindbrain
Synaptic Connection
Sensory
Neuron
Relay
Interneuron
Cerebellum
Neurons Born (E10.5 to E13.5)
Ventricular
Zone
Mantle
Zone
PM
G0
G1
M
S
G2
Early Embryonic Interneuron Populations
Foxd3 = I2
Isl1-2 =
I3
VZ
Lbx1 = I4
MZ
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
Hindbrain-Spinal
Cord Junction
Brachial
Enlargement
Cervical Region
Abdominal Region
Lumbar Region and
Enlargement
E18.5 Backfilled Spinal Cord
Dorsal
Section 27
(27 sections X 100 m
= 2.7 mm)
Ventral
1 cm
E17.5 Backfilled Spinal Cord
Dorsal
Section 10
(10 sections X 100 m
= 1.0 mm)
Ventral
1 cm
E16.5 Backfilled Lbx1 +/- Spinal Cord
Dorsal
Section 28
(28 sections X 40 m =
1.1 mm)
Ventral
1 cm
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