Lhx8 interacts with a novel germ cell-specific nuclear factor containing an Nbl1 domain in rainbow trout (Oncorhynchus mykiss)

Abstract

Lhx8 is an important transcription factor that is preferentially expressed in germ cells. Lhx8 null mice are infertile due to lack of oocytes and impairment of the transition from primordial follicles to primary follicles. Lhx8 deficiency also affects the expression of many important oocyte-specific genes. In this study, we report the characterization of rainbow trout lhx8 genes and identification of a novel germ cell-specific nuclear factor that interacts with Lhx8. Two lhx8 genes, lhx8a and lhx8b, were identified, encoding proteins of 344 and 361 amino acids, respectively. The two proteins share 83% sequence identity and both transcripts are specifically expressed in the ovary. Quantitative real time PCR analysis demonstrated that both genes are expressed highly in pre-vitellogenic ovaries as well as in early stage embryos. Using a yeast two-hybrid screening system, a novel protein (Borealin-2) interacting with Lhx8 was identified. The interaction between either Lhx8a or Lhx8b and Borealin-2 was further confirmed by a bimolecular fluorescence complementation (BiFC) assay. Borealin-2 is a protein of 255 amino acids containing an Nbl1 domain, and its mRNA expression is restricted to the ovary and testis. A GFP reporter assay revealed that Borealin-2 is a nuclear protein. Collectively, results indicate that both Lhx8a and Lhx8b function through interaction with Borealin-2, which may play an important role during oogenesis and early embryogenesis in rainbow trout.

Phycocyanin Improves Reproductive Ability in Obese Female Mice by Restoring Ovary and Oocyte Quality

“…As obesity led to an increase in the number of atretic follicles, we wondered if this increase was induced by the abnormal expressions of the genes BMP4, GDF9, or LHX8 that play key roles during ovarian follicular development (Fu et al, 2017;Liu et al, 2017;Stocker et al, 2020). Our results demonstrated that there were no significant differences in their mRNA expression levels among the three mice groups, suggesting that the increased number of atretic follicles was not caused by abnormal BMP, GDF9, and LHX8 gene expression.…”

A First Insight into the Gonad Transcriptome of Hong Kong Catfish (Clarias fuscus)

“…figla plays a key role in the early ovarian differentiation of zebrafish. In addition, the interaction between lhx8 and figla regulates the growth and differentiation of mouse oocytes [ 47 ]. In zebrafish with bmp15 knockout, gonads are normally developed at an early stage.…”

Expression profiles of cdca9 related to ovarian development in loach (Misgurnus anguillicaudatus)

“…Studies about paralogues of borealin proteins are very scarce. The expression distribution of Cdca9, the only known paralogue of borealin proteins, also known as Borealin‐2 and Dasra A, was once investigated in Oncorhynchus mykiss (Fu et al ., 2017). The paralogue is still shrouded in mystery.…”

“…The sequence and phylogenetic analysis suggested that Cdca9 was highly conserved in fish, sharing the highest level of identity with Triplophysa tibetana (80.31%), and was more similar to T. tibetana than other species in the resulting tree (Supporting Information Figure S1). Similar to borealin in vertebrates, loach Cdca9 had an Nbl1 domain which resembled in O. mykiss (Fu et al ., 2017). This domain encodes a protein that belongs to the Nbl1_Borealin_N family, containing both the N terminal region of borealin and Nbl1 (El‐Gebali et al ., 2019).…”

“…This result slightly differed from Fu et al . (2017). In their research, cdca9 was upregulated in the early embryonic development in O. mykiss , but as the embryos grow, there was a fluctuation at 13.5 h post‐fertilization, the expression of cdca9 decreased and then increased, then continued to decrease until undetectable.…”