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Casonya Matese Johnson

Associate Professor
Education

Ph.D. Biology
Johns Hopkins University 1996

Specializations

Molecular Genetics and Biochemistry
Cellular, Molecular Biology and Physiology
Neurobiology and Behavior
Post-embryonic functions for bHLH Transcription Factors in Regulating Tissue Morphogenesis, Reproduction, and Fat/Iron Metabolism

Biography

Research Description

Post-embryonic functions for bHLH Transcription Factors in Regulating Tissue Morphogenesis, Reproduction, and Fat/Iron Metabolism

Our research focuses on understanding the mechanisms of transcriptional regulation, and how these mechanisms are used to control post-embryonic development and morphogenesis, animal behavior, and physiological responses to environmental stress.  We use Caenorhabditis elegans to investigate the roles of an atypical bHLH protein family and a glia-specific bHLH protein in regulating gene expression and we seek to understand how these proteins control 1) reproduction and organ development, 2) nervous system function and development, and 3) fat storage and metabolism in larval and adult animals.

HLH-17 is glia-specific transcription factor that mediates animal behavior.  Expression of the gene encoding HLH-17 is restricted to a set of astrocyte-like glial cells that protect and support the dopaminergic neurons in hermaphrodites and males. HLH-17 regulates the expression of the D1-like and D2-like dopamine receptor genes, the dopamine reuptake transporter gene, and genes required for acetylcholine signaling.  Without HLH-17, dopamine-mediated behaviors are atypical, and hlh-17 mutants are sensitive to the norepinephrine/dopamine reuptake inhibitor bupropion, but insensitive to the dopamine antagonist, reserpine, and the serotonin reuptake transporter, fluoxetine.  Our current and future studies address the hypothesis that the HLH-17 transcriptional network modulates animal behavior by directing glia function.

The Notch-transducer protein HLH-29 coordinates animal homeostasis and reproduction.  HLH-29 is one of six dual-domain bHLH proteins in C. elegans that acts in Notch-dependent and Notch-independent events during embryogenesis. Post-embryonic roles for this protein include regulation the coordination of fat and carbohydrate metabolism with iron homeostasis. This coordination extends to the regulation of animal development and behavioral responses to the environment. Animals without HLH-29 accumulate excessive fat, have atypical oxidative stress responses, and have abnormal development of the sexual gonad. We aim to determine molecular mechanisms by which HLH-29 regulates transcription, to determine HLH-29’s placement in signaling pathways that regulate reproduction and sexual development, and to precisely define the HLH-29 transcriptional networks that direct the coordination of fat and carbohydrate metabolism with iron homeostasis.

HLH-25 is a transcriptional regulator of PTEN and of genes required for cell division and tissue morphogenesis.  HLH 25 is a second Notch-activated dual domain bHLH protein in C. elegans. The HLH-25 transcriptional network is highly enriched in genes that are required for cell cycle regulation and for cellular division during mitosis and meiosis. Interestingly, our preliminary studies indicate that HLH-25 is needed for postembryonic morphological development, as indicated by the abnormal architecture and function of the sexual gonad arm and the aberrant dauer exit phenotypes of hlh-25 mutants. Our current and future studies aim to test the hypothesis that HLH-25 connects Notch and Pten signaling to transcriptionally regulate sexual reproduction, including gamete formation, and tissue morphogenesis.

 

Lab Information

Lab Members Position Email
Casonya Johnson PI cjohnson113@gsu.edu
Stephanie Bowles PhD Student sbowles2@student.gsu.edu
Ke’Ara Brown-Smith PhD Student kbrownsmith212@gmail.com
Han Ting Chou Post-Doc hchou2@gsu.edu
Theresa Amoako Owusu PhD Student tamoako1@student.gsu.edu
Megan Wynegar MS Student mwynegar1@student.gsu.edu
India Alexandria Abdul-Salaam Undergraduate Student abdulsalaam1@student.gsu.edu

Previous Lab Members

Lab Members
Chaquetta Felton
Raymarie Gomez-Vazquez
Karl Mereus
Thai Tran
Thanh Quach
Kun Wang
Ana White

 

Publications