Abstract

Within the retina, the POU domain of transcription factors brn-3.0, brn-3.1, and brn-3.2 are present only in retinal ganglion cells. These genes are believed to be involved in establishing neural cell lineages in mammals. In this study brn-3.2 was examined by comparing the number of ganglion cells present during postnatal development in normal mice (+/+), in mice homozygous (-/-) for the brn-3.2 gene, and in adult mice with a heterozygous gene deletion (+/-) for brn-3.2. Optic nerve cross sections were imaged by electron microscopy, and axon profiles counted systematically by hand. These counts were then related to the nerve cross sectional area to obtain the total axon count per nerve. Axon counts were taken for postnatal day 0 (PO), P5, P10, and adult values. At birth (PO) the average value for the control group of mice was 136,367 (s.e. 3,317) axons whereas the average value for gene deleted mice at birth was 79,540 (s.e. 10,299) axons. The axon counts in normal mice decreased postnatally to the final average adult value of about 47,163 (s.e. 2,873) axons, similar to previously published values. In contrast, the brn-3.2 gene deleted animals decreased to mean adult values of 6,661 (s.e. 967) axons. Both the brn-3.2 (+/+) and the brn-3.2 (-/-) animals had large attrition in axon numbers throughout postnatal periods, with greater loss occurring for the gene deleted animals. Adult brn-3.2 (+/-) animals, heterozygous for the gene, had axon numbers that overlapped the range for normal adult animals.

The presence of large numbers of axons in the early postnatal brn-3.2 (-/-) animals, combined with their late postnatal loss (occurring during the normal period of axon loss), indicates that the brn-3.2 gene does not determine ganglion cell genesis. The relatively late axon loss in the brn-3.2 (-/-) animals implicate this gene in guiding or establishing axon connections with target sites in the central nervous system.

LLU Discipline

Anatomy

Department

Anatomy

School

Graduate School

First Advisor

Michael A. Kirby

Second Advisor

Paul J. McMillan

Third Advisor

Robert Schultz

Degree Name

Master of Science (MS)

Degree Level

M.S.

Year Degree Awarded

1999

Date (Title Page)

12-1999

Language

English

Library of Congress/MESH Subject Headings

Transcription Factors -- physiology; Neurons -- physiolgy; Transcription Factors -- genetics; Neurons -- cytology; Retina -- physiology; Ganglia, Sensory -- physiology; Retinal Ganglion Cells; Cell Differentiation

Type

Thesis

Page Count

vii; 74

Digital Format

PDF

Digital Publisher

Loma Linda University Libraries

Usage Rights

This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.

Collection

Loma Linda University Electronic Theses and Dissertations

Collection Website

http://scholarsrepository.llu.edu/etd/

Repository

Loma Linda University. Del E. Webb Memorial Library. University Archives

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