BCAS2 regulates granulosa cell survival by participating in mRNA alternative splicing

Abstract

Background Granulosa cell proliferation and differentiation are essential for follicle development. Breast cancer amplified sequence 2 (BCAS2) is necessary for spermatogenesis, oocyte development, and maintaining the genome integrity of early embryos in mice. However, the function of BCAS2 in granulosa cells is still unknown. Results We show that conditional disruption of Bcas2 in granulosa cells caused follicle development failure; the ratio of the positive cells of the cell proliferation markers PCNA and Ki67 were unchanged in granulosa cells. Specific deletion of Bcas2 caused a decrease in the BrdU-positive cell ratio, cell cycle arrest, DNA damage, and an increase in apoptosis in granulosa cells, and RPA1 was abnormally stained in granulosa cells. RNA-seq results revealed that knockout of Bcas2 results in unusual expression of cellular senescence genes. BCAS2 participated in the PRP19 complex to mediate alternative splicing (AS) of E2f3 and Flt3l mRNA to inhibit the cell cycle. Knockout of Bcas2 resulted in a significant decrease in the ratio of BrdU-positive cells in the human granulosa-like tumour (KGN) cell line. Conclusions Our results suggest that BCAS2 may influence the proliferation and survival of granulosa cells through regulating pre-mRNA splicing of E2f3 and Flt3l by forming the splicing complex with CDC5L and PRP19.

BCAS2 regulates oocyte meiotic prophase I by participating in mRNA alternative splicing

“…Moreover, at 5dpp, the positive TUNEL signal in cKO ovaries was significantly increased compared with that in the control, which indicated that apoptosis occurred in the primordial follicles (Figure 5G,H). In addition, our previous studies demonstrated that Bcas2 is involved in splicing precursor mRNAs through the CDC5L/PRP19 complex 25 . The fluorescence intensity of CDC5L and PRP19 with VASA was diminished in oocytes, suggesting that BCAS2 may regulate the AS of Dazl and Diaph2 through the CDC5L/PRP19 complex (Figure 5I), which in turn affects oogenesis.…”

“…Primordial follicles and primary follicles were counted and classified in every fifth section, the total number of follicles was multiplied by five. Secondary follicles and antral follicles were counted by scanning all sections, and the follicles were counted in all sections with clear oocyte nuclei 25–28 …”

“…In addition, our previous studies demonstrated that Bcas2 is involved in splicing precursor mRNAs through the CDC5L/PRP19 complex. 25 The fluorescence intensity of CDC5L and PRP19 with VASA was diminished in oocytes, suggesting that BCAS2 may regulate the AS of Dazl and Diaph2 through the CDC5L/PRP19 complex (Figure 5I), which in turn affects oogenesis. Thus, BCAS2, through the PRP19 complex, participates in Dazl and Diaph2 AS to regulate MI and primordial follicle reserve, thus influencing POI (Figure 6).…”