Molecular identification and expression of the Foxl2 gene during gonadal sex differentiation in northern snakehead Channa argus

Abstract

Channa argus is one of the most commercially important fish species in China. Studies show that males of C. argus grow faster than females at the same age. In order to explore the sex differentiation mechanism of C. argus, we isolated the full length of the sex-related gene Foxl2 cDNA and analysed its expression patterns during gonadal sex differentiation. Alignment of known Foxl2 amino acid sequences from vertebrates confirmed the conservation of the Foxl2 open reading frame, especially the forkhead domain and C-terminal region. Quantitative RT-PCR revealed that Foxl2 is predominantly expressed in brain, pituitary, gill and ovary, with its highest level in ovary but low levels in testis and other tissues, reflecting a potential role for Foxl2 in the brain-pituitary-gonad axis in C. argus. Our ontogenetic stage data showed that C. argus Foxl2 expression was significantly upregulated from 1 to 11 days posthatching (dph) and that the initiation of expression preceded the first anatomical ovarian differentiation (27 dph), suggesting that Foxl2 might play a potential role in early gonadal sex differentiation in C. argus. In addition, the Foxl2 protein was primarily located in granulosa cells surrounding the oocytes of mature C. argus, implying that Foxl2 may have a basic function in granulosa cell differentiation and the maintenance of oocytes.

Transcriptome Analyses Reveal Expression Profiles of Morphologically Undifferentiated and Differentiated Gonads of Yangtze Sturgeon Acipenser dabryanus

“…To examine the expression level of foxl2 in gonads of Amur sturgeon during morphological sex differentiation, the results also showed that sexual dimorphic expression of foxl2 was observed in morphologically differentiated gonads [10]. Similar to most other fish, foxl2 exhibits a significant sex dimorphic and ovary-dominant expression pattern [55,[58][59][60][61][62][63] and is one of the earliest known markers of ovarian differentiation [59]. In a previous work on beluga (Huso huso), the results showed that foxl2 and cyp19a1 mRNA were sexually dimorphically expressed in female gonads during gonadal sex differentiation and development [12].…”

Experimental evidence of masculinization by continuous illumination in a temperature sex determination teleost (Atherinopsidae) model: is oxidative stress involved?

“…Some key genes have been identified in the fish molecular gonad differentiation pathway, the foxl2 transcription factor can up‐regulate gonadal aromatase expression, playing a primary function in early ovarian differentiation by catalizing the synthesis of the oestradiol from testosterone (Wang et al . , , , ). In the case of males, the sox9 transcription factor is involved in early testis differentiation (Ijiri et al .…”

Cloning, Identification, and Functional Analysis of the Foxl2 Gene in Procambarus clarkii

“…The same results have been found in other fish. The Foxl2 gene is mainly expressed in the brain, gill, and ovary of Channa argus, with the highest expression level being found in the ovary and a lower expression level being found in the testis and other tissues [35]. The Foxl2 messenger RNA in catfish is expressed more significantly in the brain, pituitary gland, and ovary of females.…”