Characterizing the Role of Mammalian DEAF-1 in Reproduction, Neural Tube Closure, and Gene Expression in the Developing Embryo

Author

Sara Noraen Reardon, Southern Illinois University CarbondaleFollow

Date of Award

1-1-2008

Degree Name

Master of Science

Department

Molecular Cellular and Systemic Physiology

First Advisor

Collard, Michael

Abstract

The transcription factor DEAF-1 is the mammalian homologue of a critical Drosophila developmental gene and is essential for neonatal survival in mice. Haploinsufficiency of Deaf-1 in the testis of adult mice was initially thought to cause loss of spermatogenesis and disrupted morphology of the seminiferous tubules, and this heterozygosity was thought to be sufficient to disrupt epigenetic programming in the developing sperm to produce inheritance of testicular defects in both heterozygous and genotypically normal offspring. Although Deaf-1 knockout mice do display disrupted testis structure, infertility at advanced age, hyperproliferation of early germ cells, and abnormal staging of seminiferous tubules, this phenotype was also observed in normal mouse strains that were born in the SIUC vivarium. Mice ordered from a vendor and raised at SIUC did not show testicular defects. This suggests an environmental factor at the SIUC vivarium may act as an endocrine disruptor during embryonic testicular development. Deaf-1-/- mice die soon after birth, often as the result of exencephaly, a gross neural tube defect (NTD). Unlike many mouse models, exencephalic Deaf-1-/- mice do not display a higher incidence of NTDs in females as compared to their male littermates. DEAF-1 promotes Bax-mediated apoptosis; studies using terminal UTP nick-end labeling (TUNEL) suggest a global increase in apoptosis in both exencephalic and normal Deaf-1-/- fetuses during neurulation as compared to their Deaf-1+/+ littermates. This indicates that Deaf-1 is crucial for correct apoptotic patterning during development, which, in turn, is essential for neural tube closure. Finally, cDNA microarray comparison of e14.5 Deaf-1 knockout and wildtype fetuses reveals expression of translation initiation factor 4g3 (Eif4g3) to be downregulated in Deaf-1-/- fetuses. Electrophoretic mobility shift assay using recombinant DEAF-1, and chromatin immunoprecipitation assay of a human cell line confirmed DEAF-1 could bind the eIF4G3 promoter both in vitro and in vivo. Additionally, transcription of the Deaf-1 Antisense Transcript (Das) was found to be significantly downregulated in both e14.5 fetuses and e18.5 fetal brains from Deaf-1-/- mice, suggesting that either lack of Deaf-1 protein or lack of exons 2 through 5 in Deaf-1 knockout mice causes changes in levels of the noncoding RNA that shares Deaf-1's promoter in the mouse.