Abstract
BackgroundThe LIM domain protein Fhl5 was previously found to interact with CREM, a DNA binding transcriptional regulator necessary for spermiogenesis in mammals. Co-transfection 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.MethodsTo 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.ResultsWeak 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.ConclusionThe 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.
Highlights
The LIM domain protein Fhl5 was previously found to interact with CREM, a DNA binding transcriptional regulator necessary for spermiogenesis in mammals
We conclude that Flh5's role in sperm maturation and morphology is partially sensitive to the genetic background it is investigated in
Flh5 is not essential for testicular gene expression in adult mice In the first experiment we compared two testicular samples from non-isogenic Fhl5 mutant and wild-type mice at the age of 9-10 weeks and identified among 45101 probe sets a set of 23222 cases displaying signals greater than 5.5, the median of the normalized log2 intensity values which we considered the cut-off for reliably detectable expression
Summary
The LIM domain protein Fhl was previously found to interact with CREM, a DNA binding transcriptional regulator necessary for spermiogenesis in mammals. Sexual reproduction of male mammals requires genes involved in meiosis, sperm formation and maturation as well as fertilization many of which are controlled by developmental stage-specific transcription factors [1,2]. Using a yeast twohybrid assay CREM was shown to bind Fhl which is expressed in meiotic spermatocytes and highly induced in post-meiotic round spermatids. The protein was shown to mediate strong reporter gene expression in transfection assays using heterologous promoter constructs in yeast and mammalian cells and its dynamic pattern of nuclear and cytoplasmic localization during early and late stages of spermiogenesis is mediated via direct interaction with the Kif17b kinesin motor protein [10,11,12,13]. Fhl expression in pachytene spermatocytes and round spermatids was proposed to be dependent upon CREM in rodents and in human; weak transcription of Fhl was found in three out of four infertile patients whose testes contained meiotic germ cells normally expressing the gene, suggesting a link between impaired Fhl function and spermatogenic arrest in a subgroup of individuals [15,16,17,18]
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