Areas of Interest
Spermatogenesis is a complex process requiring extensive changes in the chromatin and epigenetic landscape for proper specification and differentiation. Aberrations in this process can lead to infertility, a major health problem worldwide, affecting 1 in every 6 couples. Approximately 50% of the infertility cases lack a clear etiology. Therefore, a greater understanding of the molecular mechanism / pathways required for proper germ cell development is required to develop effective treatments or alternative therapies to restore spermatogenesis. To achieve this goal the Hammoud laboratory will emphasize on two areas summarized below:
1) In-vitro gametogenesis:
Spermatogenesis requires a complex integration of intrinsic/extrinsic factors to execute the full/normal developmental process. Here, we aim to use single cell high throughput genomics and super resolution microscopy to define intrinsic and extrinsic (niche) factors that maybe important for maintaining spermatogenesis both in-vivo and/or in-vitro. A greater understanding of the normal gametogenesis process will provide a foundation for understanding how changes either in microenvironment or germ cell can lead to male infertility. Reconstitution of this process in-vitro either from pre-pubertal/adult germ stem cells or through the use of induced pluripotent stem cells will be transform the lives of many individuals.
2) Sperm Epigenome and its role in development and disease:
Unlike somatic cells, the sperm genome is packaged in histones and protamines. Whether this unique chromatin landscape is a remnant of gametogenesis or instructive for development is unknown. The lab has developed novel strategies to explore the role and significance of these proteins in spermatogenesis and development.
Honors & Awards
2012-2015 – The Helen Hay Whitney Postdoctoral Fellowship
2014-present – RSP and Organogenesis Scholar
2016-2021 - NIH Director's New Innovator Award
2012-2014 Post-doctoral fellow, Huntsman Cancer Institute, University of Utah
2005-2011 Ph.D., Molecular Biology/Physiology Huntsman Cancer Institute, University of Utah
2004 B.S., Biological Sciences Wayne State University
Published Articles or Reviews
Hammoud SS, Nix DA, Zhang H, Purwar J, Carrell DT*, Cairns BR* (2009): Distinctive chromatin in human sperm packages genes for embryo development. Nature, 460:473-9.
Hammoud SS, Nix DA, Hammoud AO, Gibson M, Cairns BR, Carrell DT (2011). Genomewide analysis identifies changes in histone retention and epigenetic modifications at developmental and imprinted gene loci in the sperm of infertile men. Hum Reprod. 26 (9):2558-69.
Hammoud SS, Low D, Yi C, Carrell DT, Guccione E* and Cairns BR* (2014). Chromatin Strategies for Maintaining Pluripotency in Adult Germline Stem Cells and Mammalian Spermatogenesis. Cell Stem Cell. 2014 Aug 7;15(2):239-53.
Hammoud SS*, Low DH, Yi C, Lee CL, Oatley JM, Payne CJ, Carrell DT, Guccione E*, Cairns BR*. Transcription and imprinting dynamics in developing postnatal male germline stem cells. Genes Dev. 2015 Nov 1;29(21):2312-24.