Functional analysis of the SRY-KRAB interaction in mouse sex determination.
BACKGROUND
SRY (sex-determining region Y), the master regulator of male development in mammals, has been studied extensively for more than 17 years, but how the SRY protein triggers the chain of events leading to testis development remains unclear. SRY probably requires a partner protein to elicit its molecular function. KRAB-O, a novel protein containing a KRAB (Krüppel-associated box) domain only, was suggested recently as a candidate SRY partner. In order to investigate the possible role of KRAB-O in sex determination, we studied its expression and conducted functional assays of the SRY-KRAB interaction.


RESULTS
More than 100 KRAB genes were found to be expressed in mouse developing gonads, including 19 transcripts encoded by the KRAB-O cluster that were found to be expressed in somatic cells at 11.5 dpc (days post-coitum). Loss-of-function analysis in Sry-expressing cultured cells, using shRNA (small hairpin RNA) constructs directed against KRAB-O and its homologous genes, resulted in a reduced ability to up-regulate Sox9 [SRY-related HMG (high-mobility group)-box 9]; however, KRAB-knockdown mice exhibited normal testis development.


CONCLUSIONS
Reduced Sox9 expression in KRAB-knockdown cells supports a role for KRAB-O and perhaps other KRAB genes in mediating SRY function. Overlapping expression and potential redundancy between members of the large KRAB-O gene cluster may mask any loss-of-function in vivo, presenting clear challenges for further functional analysis.
Polanco
Juan Carlos
JC
Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia.
Wilhelm
Dagmar
D
Mizusaki
Hirofumi
H
Jackson
Andrew
A
Browne
Catherine
C
Davidson
Tara
T
Harley
Vincent
V
Sinclair
Andrew
A
Koopman
Peter
P
D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D011485:Protein Binding / Q000502:physiology; D034741:RNA, Small Interfering / Q000494:pharmacology; D055758:SOX9 Transcription Factor / Q000235:genetics*; D019849:Sex Determination Processes; D051876:Sex-Determining Region Y Protein / Q000378:metabolism* / Q000502:physiology; D013737:Testis / Q000254:growth & development; D015854:Up-Regulation / Q000235:genetics
D002352:Carrier Proteins; C534242:KRAB-O protein, mouse; D034741:RNA, Small Interfering; D055758:SOX9 Transcription Factor; D051876:Sex-Determining Region Y Protein; C527933:Sox9 protein, mouse; C497746:Sry protein, mouse