Critical roles of the ddx5 gene in zebrafish sex differentiation and oocyte maturation

Abstract

DEAD-box helicase 5 (Ddx5) functions as an ATP-dependent RNA helicase and as a transcriptional coactivator for several transcription factors; however, the developmental function of the ddx5 gene in vertebrates is not fully understood. We found that the zebrafish ddx5 gene was expressed in developing gonads. Using the genome editing technology transcription activator-like effector nuclease, we established a ddx5-disrupted zebrafish and examined the morphological phenotypes of the mutant. We found that the majority of ddx5-deficient mutants developed as fertile males with normal testes and a small number of ddx5-deficient mutants developed as infertile females with small ovaries. Apoptotic cell death at 31 days post fertilization was increased in thick immature gonads (presumptive developing ovaries) of the ddx5-deficient mutant compared to those of heterozygous wild-type fish, while the number of apoptotic cells in thin immature gonads (presumptive developing testes) was comparable between the mutant and wild-type animals. Histological analysis revealed that ovaries of adult ddx5-deficient females had fewer vitellogenic oocytes and a larger number of stage I and II oocytes. The amount of cyclic adenosine monophosphate in the ddx5-deficient ovaries was high compared to that of wild-type ovaries, presumably leading to the mitotic arrest of oocyte maturation. Therefore, the ddx5 gene is dispensable for testis development, but it is essential for female sex differentiation and oocyte maturation in zebrafish.

Circular RNA PUM1 performs as a competing endogenous RNA of microRNA-340-5p to mediate DEAD-box helicase 5 to mitigate cerebral ischemia-reperfusion injury

“…DDX5 is a member of the DEAD-box RNA helicase family, which controls ribonucleoprotein formation [ 42 ]. DDX5 normally functions by performing as a transcriptional co-activator of several transcription factors and has been shown to motivate tumorigenesis and cancer progression [ 43 , 44 ]. Furthermore, under hypoxic conditions, DDX5 is elevated by miR-462 and restrains cell advancement by blocking cell cycle progression of DNA replication [ 45 ].…”

Regulatory roles of Bxy-laf-1 in reproductive behaviour of Bursaphelenchus xylophilus

“…The lack of Bxy-laf-1 significantly reduced the female to male sex ratios of B. xylophilus . Related genes of the DEAD-box family are involved in sex differentiation in C. elegans ( Hubert and Anderson, 2009 ), zebrafish ( Sone et al, 2020 ) and channel catfish ( Tian et al, 2017 ). Our results found that after Bxy-laf-1 dsRNA interfered with B. xylophilus , the ratio of female to male in F0 and F1 generations was significantly reduced, indicating that Bxy-laf-1 is involved in the development of sexual differentiation in B. xylophilus .…”

Sexually Dimorphic Gene Expression in X and Y Sperms Instructs Sexual Dimorphism of Embryonic Genome Activation in Yellow Catfish (Pelteobagrus fulvidraco)

“…Gata6 is expressed in the ovary during embryonic development and is crucial for follicle assembly, granulosa cell differentiation, postnatal follicle growth, and the luteinization [ 68 ], while Ddx5 is expressed by spermatogonia in mice and acts as a transcriptional co-activator in the germline maintenance [ 55 ]. In zebrafish, ddx5 was expressed in developing gonads, and it is dispensable for testes development but essential for female sex differentiation and oocyte maturation [ 69 ]. In this study, ddx5 was differentially expressed at the bud stage with much higher expression in XX females, which suggests that this gene is more important to the development of female yellow catfish.…”