As a faculty member in the Biomedical Sciences department, an active and viable research group is an important component of my job. The question of how the two genders are produced, wanting to know how this ‘decision’ is made at the molecular level has been a major focus of my research interest and career. A few years ago, we discovered a link between the RNA silencing machinery and the master switch gene which controls the determination of sexual identity in fruit flies. In trying to understand how it is that RNA silencing affects the fruit fly sex determination process we have come to appreciate the role of the state of chromatin in developmental decisions. We now use this well-established system to understand how RNA silencing regulates and fine-tunes a developmental pathway; this work is driving us to understand the less appreciated role of the RNA silencing machinery in the nucleus.
Conducting research includes the training and teaching of graduate students. We also have undergraduates in the laboratory, exposing them to the concepts and requirements of research. More formal teaching involves courses at the graduate level which are usually team-taught and are in the areas of molecular biology, biochemistry or genetics. Another responsibility is to participate in the mentoring and teaching of our medical students.
I have also served as the Assistant Graduate Program director in the Biomedical Sciences department, from March 2010 to August 2015.
Jamila Horabin came to the United States on an International Scholarship to Duke University in Durham, N.C. After getting her bachelor's degree, she stayed on at Duke for her Ph.D. Courses during the graduate years made a lasting impression of the idea that development could be understood at the level of molecules. Toward this goal, she decided to work on Drosophila as the model system.
B.A., Duke University. Major: Chemistry. Summa Cum Laude. (1981)
Ph.D, Duke University. Major: Biochemistry, Genetics. Supervisor: Robert Webster, Ph.D.(1987)
Postdoctoral training, Department of Molecular Biology, Princeton University, Princeton, N.J. Mentor: Paul Schedl, Ph.D. (1988–1993)
FSU University Committees
Member, Graduate Policy Committee (2009–present).
FSU College Committees
Member Council of Diversity and Inclusion (2011 - present)
Member, COM Liaison Committee on Medical Education Accreditation, Faculty Subcommittee (2010–2011).
Member, COM Medical Student Admissions Committee (2006–2013).
FSU Department Committees
Biomedical Sciences Executive Committee (2011 - 2015)
Member, Faculty Search Committee (2009).
Member, Graduate Program Committee (2009–2015).
Member, Faculty Evaluation Committee (2009).
Chair, Graduate Admissions Committee (2008).
Member, Faculty Development Committee (2005, 2013, 2014).
Elected member, Faculty Tenure Committee (2005).
Promotion and Tenure Committee (2011-2013)
Member, Graduate Program Committee (2005).
Member, Graduate Curriculum Committee (2005–2007).
FSU Program Committees
Assistant Director, Graduate Program, Biomedical Sciences Department, College of Medicine (2010–2015).
Outstanding Senior Faculty Researcher, FSU College of Medicine (2011).
Honor Roll Award, American Cancer Society (2001).
Phi Beta Kappa, Duke University (1981).
Graduate Scholarship (1981).
Cranmer Memorial Scholarship (1980).
Class Honors (1980).
Phi Lambda Upsilon (1980).
Phi Eta Sigma, Freshman Honor Society (1979).
Duke International Scholar, Duke University (1978).
Genetics Society of America.
Association of American Medical Colleges.
Our research uses the model system Drosophila melanogaster and studies the processes of chromatin modifications, gene expression and sex determination. Much of our work in the past revolved around understanding the regulation of expression of the sex-determination master switch gene, Sex-lethal (Sxl), as it is regulated by an exquisite dose sensitive mechanism. Its activation determines female identity while male development is the default, and the sensitive nature of its regulation can be leveraged through genetics to identify regulatory components. Over the years, we have contributed toward understanding how:
• Regulated splicing of Sxl mRNA occurs.
• Sxl protein functions to generate sexually dimorphic body size.
• Early X chromosome gene dose expression affects the sex determination process.
Current research in the lab is aimed at understanding the role of the RNA silencing machinery in the process of sex determination. Females show a greater need than males for RNA silencing components, to robustly determine their sex. We hope to learn more about RNA silencing using sex determination as the readout, placing our understanding in the context of a developmental process. Projects to understand the nuclear role of the RNA silencing machinery are also ongoing. Our research has been funded by NIH.
Cabrera, J. R., Olcese, U. and Horabin, J. I. A balancing act: heterochromatin protein 1a and the Polycomb group coordinate their levels to silence chromatin in Drosophila (2015). Epigenetics and Chromatin 8:17. PMID: 25954320
Mulvey, B.B., Olcese, U., Cabrera, J. R. and Horabin, J. I. An Interactive network of long non-coding RNAs facilitates the Drosophila sex determination decision. (2014). Biochimica et Biophysica Acta Gene Reg. Mech. 1839L: 773–784. PMID: 24954180
Horabin, J. I. Long noncoding RNAs as metazoan developmental regulators (2013). Chromosome Res epub DOI 10.1007/s10577-013-9382-8. PMID: 24150236
Horabin, J. I. Balancing sex chromosone expression and satisfying the sexes. Fly 6(1). PMID: 22388008
Kappes, G., Deshpande, G., Mulvey, B. B., Horabin, J. I., & Schedl, P. (2011). The Drosophila Myc gene, diminutive, is a positive regulator of the Sex-lethal establishment promoter, Sxl-Pe. Proc Natl Acad Sci U S A, 108(4), 1543-8.
Li, H., Rodriguez, J., Yoo, Y., Shareef, M. M., Badugu, R., Horabin, J. I., & Kellum, R. (2011). Cooperative and antagonistic contributions of two heterochromatin proteins to transcriptional regulation of the Drosophila sex determination decision. PLoS Genet, 7(6), e1002122.
Gladstein, N., McKeon, M. N., & Horabin, J. I. (2010). Requirement of male-specific dosage compensation in Drosophila females – implications of early X chromosome gene expression. PLoS Genetics, 6 (7), e1001041.
Walthall, S. L., Moses, M., & Horabin, J. I. (2007). A large complex with both Patched and Smoothened initiates Hedgehog signaling in Drosophila. J. Cell Science, 120, 826-837.
Horabin, J. I. (2005). Splitting the Hedgehog signal: Sex and Patterning in Drosophila. Development, 132, 4801-4810.
Horabin, J. I., Walthall, S., Vied, C., & Moses, M. (2003). A Positive role for Patched in Hedgehog signaling revealed by the intracellular trafficking of Sex-lethal, the Drosophila Sex Determination Master Switch. Development, 130, 6101-6109.
Vied. C., Halachmi, N., Salzberg, A., & Horabin, J. I. (2003). . Antizyme is a Target of Sex-lethal in the Drosophila Germline and appears to act downstream of Hedgehog to regulate Sex-lethal and Cyclin B. Developmental Biology, 253, 214-229.
Vied, C., & Horabin, J. I. (2001). A new target for Hedgehog: the sex determination masterswitch, Sex-lethal, responds to Hedgehog signaling in the Drosophila germline. Development, 128, 2649-2660.
Waterbury, J., Horabin, J. I., Bopp, D., & Schedl, P. (2000). Sex determination in the Drosphila germline is dictated by the sexual identity of the surrounding soma. Genetics, 155, 1741-1756.
Bopp, D., Calhoun, G., Horabin, J. I., Samuels, M. E., & Schedl, P. (1996). Sex specific control of Sex-lethal is a common mechanism for sex determination in the Genus Drosophila. Development, 122, 971-982.
Horabin, J. I., & Schedl, P. (1996). Splicing of the Drosophila Sex-lethal early transcripts involves exon skipping that is independent of Sex-lethal protein. RNA, 2, 1-10.
Horabin, J. I., Bopp, D., Waterbury, J., & Schedl, P. (1995). Selection and Maintenance of Sexual Identity in the Drosophila germline. Genetics, 141, 1521-1535.
Lantz, V., Chang, J., Horabin, J. I., Bopp, D., & Schedl, P. (1994). The Drosophila orb RNA-Binding Protein is required for the formation of the Egg Chamber and establishment of Polarity. Genes & Development, 8, 598-613.
Horabin, J. I., & Schedl, P. (1993). Sex-lethal autoregulation requires multiple cis-acting elements upstream and downstream of the male exon and appears to pivot primarily on the male exon 5' splice site. Mol. Cell Biol, 13, 7734-7746.
Bopp, D., Horabin, J. I., Lersch, R. A., Cline, T. W., & Schedl, P. (1993). . Expression of the Sex-lethal gene is controlled at multiple levels during Drosophila Oogenesis. Development, 118, 797-812.
Horabin, J. I., & Schedl, P. (1993). Regulated splicing of the Drosophila Sex-lethal male exon involves a blockage mechanism. Mol. Cell Biol, 13, 1408-1414.
Bell, L. R., Horabin, J. I., Schedl, P., & Cline, T. W. (1991). Positive Autoregulation of Sex-lethal by Alternative Splicing Maintains the Female Determined State in Drosophila. Cell, 65, 229-239.
Horabin, J. I. (Ed.). (2007). Methods in Molecular Biology: Hedgehog Signaling Protocols. Humana Press, Totowa, NJ 07512.