Date of Award

Spring 5-10-2014

Degree Type


Degree Name

Master of Science (MS)



First Advisor

Casonya Matese Johnson, PhD

Second Advisor

Margo Ann Brinton, PhD

Third Advisor

Walter William Walthall, PhD


The REF-1 family proteins are distinguished by the presence of two basic helix-loop helix domains. The REF-1 family members are considered functional homologs of the Hairy/Enhancer of Split in humans. HLH-25 is one of the six members of the REF-1 family. HLH-25 has not been studied extensively. In preliminary studies from our laboratory, genes identified by microarray analysis of hlh-25 mutants were essential for embryogenesis, larval development, and growth. Thus, the present study was designed to further characterize HLH-25 and to more precisely define its role during embryonic and larval development. The gene encoding HLH-25 is actively expressed in embryos, larvae and adults. In the absence of hlh-25, animals show a 54% embryonic lethality, a reduced brood size, an increased number of unfertilized eggs, a slower movement rate, a longer life span, and a longer dauer recovery. The human tumor suppressor PTEN homolog, daf-18 is one of the HLH-25 target genes. The regulation of daf-18 through HLH-25 is the responsible for changes to the life span and dauer recovery in hlh-25 mutant animals.

Available for download on Monday, April 25, 2016