Downregulation of reproductive homeobox gene 6 (RHOX6) interferes with male germ cell differentiation

Homeodomain proteins contain a 60 amino acid DNA binding motif called homeobox that regulates a variety of developmental events. Recently, a novel cluster of homeobox genes has been discovered on the X chromosome of the mouse. Because of their selective expression in reproductive organs, they are named Reproductive homeobox genes on the X chromosome (Rhox). Rhox6, a member of the Rhox family, is expressed in primordial germ cells (PGCs) in the developing gonad and the placenta, although the biological function of Rhox6 in determination of PGCs and placental cells remains unknown. To investigate the Rhox6 function, we generated male chimeras by injection of the gene-trapped embryonic stem cells (ESCs) harboring a hypomorphic mutation in Rhox6 into wild-type blastocysts. Almost all of the male chimeras exhibited dramatically reduced fertility associated with smaller testes, reduced sperm number and motility and abnormal morphology of the epididymal sperm. To obtain a better understanding of the Rhox6 function in germ cell differentiation, we took advantage of in vitro ESC culture. ESCs can differentiate into PGCs when ESCs are cultured as aggregates called embryoid bodies (EBs). By using a mouse ESC line that expresses the enhanced green fluorescent protein (EGFP) under the promoter of Oct3/4, a central regulator of cellular pluripotency, the presence of PGCs within EBs was monitored in real time by EGFP expression. While this ESC line was induced to differentiate into PGCs, expression of Rhox6 was downregulated by stable expression of the short-hairpin (sh) RNA against the Rhox6 transcripts and we found that continuous downregulation of Rhox6 expression resulted in dramatic decrease in the number of germ cells differentiated. Collectively, these results suggest that downregulation of Rhox6 impairs differentiation of PGCs.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Animal Sciences

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2011

Author dc:creator

• Liu, Chang

Contributors dc:contributor

• Tanaka, Tetsuya S.

• Rhox6
• embryonic stem cells
• downregulation
• germ cell differentiation

Statement dc:rights

• Copyright 2010 Chang Liu

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/18608

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/18608