Involvement of pax2 in ovarian development and recrudescence of catfish: a role in steroidogenesis

Abstract

PAX2, a member of paired box family, is an essential transcription factor for the organ development in vertebrates including teleosts, yet no evidence has been shown for its involvement in reproduction. To study this, partial- and/or full-length cDNA of pax2 was isolated from the ovary of catfish, Clarias batrachus, along with its other Pax family members, pax1 and pax9 Tissue distribution and ontogeny expression analysis indicated the prevalence of pax2 but not pax1 and pax9 in ovary. Varied phase-wise expression during ovarian cycle and elevation of pax2 after human chorionic gonadotropin induction showed probable regulation by gonadotropins. Pax2 could be localized in various stages of oocytes and in follicular layer of vitellogenic and post-vitellogenic oocytes. To assess the functional significance of pax2, transient RNA silencing was performed using primary catfish ovarian follicle culture, in vitro, and in catfish, in vivo, through ovary-targeted injection of PEI-esiRNA. Pax2 siRNA treatment reduced the expression of various transcripts related to ovarian development like signaling molecules such as wnt4 and wnt5, estrogen receptors, several steroidogenic enzymes and transcription factors. These transitions in transcript levels might have been mediated by Pax2 acting upstream of wnt4/5 that may play a role in steroidogenesis and/or ovarian development along with ad4bp/sf-1 or by direct or indirect interaction with steroidogenic enzyme genes, which is evident from the change in the levels of serum estradiol-17β but not 17α,20β-dihydroxy-4-pregnen-3-one. Taken together, it seems that pax2 has a plausible role during ovarian development and/or recrudescence of catfish either directly or indirectly through Wnt signaling pathway.

Diverse phenotypes in children with PAX2‐related disorder

“…First, we reported some rare extrarenal phenotypes involved multiple systems in our patients including skeletal deformity (fourth metatarsal microsomia), ovarian teratoma, and congenital ventricular septal defect. PAX2 may be involved in the development of the skeleton and ovary, and in heart morphogenesis (Prathibha & Senthilkumaran, ; Röttinger et al, ; Wang, Lan, Cho, Maltby, & Jiang, ). Only one child had previously been reported with a PAX2 mutation and a skeletal deformity (congenital camptodactyly) (Liu, Wang, Huang, & Yu, ).…”

Candidate gene identification of ovulation-inducing genes by RNA sequencing with an in vivo assay in zebrafish

“…The paired box gene ( pax2a ) encodes a transcription factor. It is expressed in the ovary of catfish, and has been speculated to be an up-stream regulator of the Wnt signaling pathway [ 38 ]. Pax2a also plays roles in maintaining the primordium and in the differentiation of thyroid follicles in zebrafish during early embryogenesis [ 39 ].…”

Advances in Reproductive Endocrinology and Neuroendocrine Research Using Catfish Models

“…In many animal models including catfish, RNA knockdown can be achieved more feasibly using siRNA, shRNA or esiRNA. In this line, in vivo and in vitro transient gene silencing using PEI mediated siRNA/shRNA/esiRNA has been standardized and well established at tissue and cellular levels in gonads and brain as well as at animal level in our laboratory using various fish models including catfish [ 67 , 85 , 136 , 165 , 188 , 220 , 221 ] to functionally characterize many important factors related to teleostean reproduction. In addition, Senthilkumaran [ 168 ] compared mammalian and piscine oocyte maturation with a note on sperm maturation citing the involvement of hsd20b vis-à-vis 17α,20β-DP in addition to T and 11-KT [ 140 , 222 ].…”