Fhl5/Act, a CREM-binding transcriptional activator required for normal sperm maturation and morphology, is not essential for testicular gene expression Reproductive Biology and Endocrinology 2009, 7:133 doi:10.1186/1477-7827-7-133

Background: the LIM domain protein Fhl5 was previously found to interact with CREM, a DNA binding transcriptional regulator necessary for spermiogenesis in mammals. Cotransfection experiments using heterologous promoter constructs indicated a role for Fhl5 in transcriptional up-regulation of CREM-dependent testicular genes. Male mice lacking Fhl5 were reported to be fertile but displayed partially abnormal sperm maturation and morphology. Methods: to identify Fhl5 testicular target genes we carried out two whole-genome expression profiling experiments using high-density oligonucleotide microarrays and total testis samples from Fhl5 wild-type versus homozygous mutant mice first in different and then in isogenic strain backgrounds. Results: weak signal differences were detected in non-isogenic samples but no statistically significant expression changes were observed when isogenic Fhl5 mutant and wild-type samples were compared. Conclusions: the outcome of these experiments suggests that testicular expression profiling is extremely sensitive to the genetic background and that Fhl5 is not essential for testicular gene expression to a level detected by microarray-based measurements. This might be due to redundant function of the related and similarly expressed protein Fhl4.