Differential <i>DMRT1</i> Expression in the Gonads of <i>Podarcis sicula</i> (Reptilia: Lacertidae)

Abstract

DMRT genes encode a large family of transcription factors which share an unusual cysteine-rich DNA-binding motif, the DM domain. DM family members have been studied in the context of sexual development; in particular, the DMRT1 gene appeared to be the one most directly involved in sex determination, but its activity is largely unexplored and possible downstream targets of this factor have yet to be identified. DMRT1 of the lacertid lizard Podarcis sicula (PsDMRT1) was isolated as a model to study differential gene expression during the seasonal reproductive cycle of an ectothermal species. The adult testis of P. sicula exhibits full activity in spring, complete regression in summer and a slow autumnal recrudescence without spermiation. We cloned a 591-bp partial ORF of the PsDMRT1 fragment, whose putative amino acid sequence contains the conserved DM domain. Northern blot analysis of mRNA from different tissues of P. sicula individuals captured in spring demonstrated DMRT1 transcripts only in testis. Semi-quantitative RT-PCR and in situ hybridization experiments showed peak PsDMRT1 expression in spring, lower expression in autumn and no expression during the period of gonad regression. A possible correlation between androgen level variations and PsDMRT1 transcripts is hypothesized and discussed. Finally, data showed that PsDMRT1 is expressed only in spermatogenic cells, before the second meiotic division, suggesting that its role is confined to the proliferation and maintenance of spermatogonia and spermatocytes.

Expression of Genes Controlling Testicular Development in Adult Testis of the Seasonally Breeding Iberian Mole

“…Here we report that mole spermatogonia show the same DMRT1 expression pattern, suggesting that testosterone might regulate the expression of DMRT1 in germ cells indirectly, by modulating Sertoli cell function. Fourth, in the seasonal breeding lizard Podarcis sicula , DMRT1 is expressed only in the breeding season, coinciding with the seasonal peak in testosterone levels [Capriglione et al, 2010]. According to these observations, we hypothesize that intratesticular levels of testosterone could control the circannual variations of the spermatogenic activity in seasonal breeders by modulating the expression of DMRT1 and thus the proliferation rate in spermatogonial cells.…”

“…In mice, Dmrt1 is expressed in pre-meiotic primordial germ cells of the postnatal testis, while, in the adult testis, Dmrt1 is expressed in spermatogonia [Lei et al, 2007]. In addition, DMRT1 is also expressed in testes of adult birds [Shan et al, 2000], reptiles [Capriglione et al, 2010], amphibians [Shibata et al, 2002] and fishes [Marchand et al, 2000]. Furthermore, germ cell-specific ablation of Dmrt1 in mice revealed that it is necessary for mitotic reactivation and survival of germ cells beyond the first postnatal week [Kim et al, 2007].…”

Transcriptional evolution underlying vertebrate sexual development

“…Approaches to understand the composition, regulation, and evolution of the regulatory network underlying sexual development include classical developmental biology methods using mutagenesis in model systems to uncover the effect of mutated genes compared to wild type phenotypes (Arboleda and Vilain, ), while studies in non‐model organisms have relied mainly on finding orthologs of the genes originally identified in model systems and comparing the expression patterns (Valleley et al, ; Smith et al, ; Bergeron et al, ; Spotila et al, ; Western et al, ; Rhen and Crews, ; Torres‐Maldonado et al, ; Murdock and Wibbels, ; Shoemaker et al, ; Hoshi and Nakao, ; Capriglione et al, ; Valenzuela, ). Leveraging more modern genomic technologies permits the de novo interrogation of transcriptomes in non‐model systems to uncover species‐specific candidate genes involved in sexual development (Munger et al, ; Hale et al, ).…”

The roles of Dmrt (Double sex/Male-abnormal-3 Related Transcription factor) genes in sex determination and differentiation mechanisms: Ubiquity and diversity across the animal kingdom

“…Except for ovary, the organ-level gene expression pattern has only been tested in male adult frogs; thus, we lack detailed information on the expression of Dmrt1 in males versus females. The expression patterns vary according to the gene and organs considered [50][51][52]. However, as these studies used RT-PCR, not quantitative-RT-PCR, the relative expression levels should be interpreted with caution.…”