BCAS2 Regulates Delta-Notch Signaling Activity through Delta Pre-mRNA Splicing in Drosophila Wing Development

BCAS2 Participates in Insulin Synthesis and Secretion via mRNA Alternative Splicing in Mice

Insulin secreted by pancreatic β cells is essential for maintaining blood glucose levels. Diabetes is caused primarily by a loss of β cells or impairment of β-cell function. A previous whole-transcriptome analysis of islets from a type 2 diabetes group and a control group showed that a splicing disorder occurred in approximately 25% of splicing events. Breast carcinoma amplified sequence 2 (BCAS2) is a spliceosome component whose function in islet β cells is unclear. Here, we report that knockdown of Bcas2 decreased glucose- and KCl-stimulated insulin secretion in the NIT-1 cell line. Pancreas weight, glucose tolerance, and insulin sensitivity were measured in normal chow-fed Bcas2 f/f-βKO mice, and β-cell mass and islet size were analyzed by immunohistochemistry. Glucose intolerance developed in Bcas2 f/f-βKO mice, but there were no significant differences in pancreas weight, insulin sensitivity, β-cell mass, or islet size. Furthermore, observation of glucose-stimulated insulin secretion and insulin secretion granules in normal chow-fed mice revealed that the insulin level in serum and the number of insulin secretion granules were decreased in Bcas2 f/f-βKO mice. These differences were related to abnormal splicing of Syt7 and Tcf7l2 pre-mRNA. Taken together, these results demonstrate that BCAS2 is involved in alternative splicing during insulin synthesis and secretion.

Molecular characterization, expression patterns and cellular localization of BCAS2 gene in male Hezuo pig

Background

Breast carcinoma amplified sequence 2 (BCAS2) participates in pre-mRNA splicing and DNA damage response, which is implicated in spermatogenesis and meiosis initiation in mouse. Nevertheless, the physiological roles of BCAS2 in the testes of large mammals especially boars remain largely unknown.

Methods

In this study, testes were collected from Hezuo pig at three development stages including 30 days old (30 d), 120 days old (120 d), and 240 days old (240 d). BCAS2 CDS region was firstly cloned using RT-PCR method, and its molecular characteristics were identified using relevant bioinformatics software. Additionally, the expression patterns and cellular localization of BCAS2 were analyzed by quantitative real-time PCR (qRT-PCR), Western blot, immunohistochemistry and immunofluorescence.

Results

The cloning and sequence analysis indicated that the Hezuo pig BCAS2 CDS fragment encompassed 678 bp open reading frame (ORF) capable of encoding 225 amino acid residues, and possessed high identities with some other mammals. The results of qRT-PCR and Western blot displayed that BCAS2 levels both mRNA and protein were age-dependent increased (p < 0.01). Additionally, immunohistochemistry and immunofluorescence results revealed that BCAS2 protein was mainly observed in nucleus of gonocytes at 30 d testes as well as nucleus of spermatogonia and Sertoli cells at 120 and 240 d testes. Accordingly, we conclude that BCAS2 is critical for testicular development and spermatogenesis of Hezuo pig, perhaps by regulating proliferation or differentiation of gonocytes, pre-mRNA splicing of spermatogonia and functional maintenance of Sertoli cells, but specific mechanism still requires be further investigated.

New insights into the centrosome-associated spliceosome components as regulators of ciliogenesis and tissue identity

Biomolecular condensates are membrane-less assemblies of proteins and nucleic acids. Centrosomes are biomolecular condensates that play a crucial role in nuclear division, cytoskeletal remodeling, and cilia formation in animal cells. Spatial omics technology is providing new insights into the dynamic exchange of spliceosome components between the nucleus and the centrosome/cilium. Intriguingly, centrosomes are emerging as cytoplasmic sites for information storage, enriched with RNA molecules and RNA-processing proteins. Furthermore, growing evidence supports the view that nuclear spliceosome components assembled at the centrosome function as potential coordinators of splicing subprograms, pluripotency, and cell differentiation. In this article, we first discuss the current understanding of the centrosome/cilium complex, which controls both stem cell differentiation and pluripotency. We next explore the molecular mechanisms that govern splicing factor assembly and disassembly around the centrosome and examine how RNA processing pathways contribute to ciliogenesis. Finally, we discuss numerous unresolved compelling questions regarding the centrosome-associated spliceosome components and transcript variants within the cytoplasm as sources of RNA-based secondary messages in the regulation of cell identity and cell fate determination. This article is categorized under: RNA-Based Catalysis > RNA Catalysis in Splicing and Translation RNA Interactions with Proteins and Other Molecules > RNA-Protein Complexes RNA Processing > Splicing Regulation/Alternative Splicing RNA Processing > RNA Processing.

BCAS2 regulates granulosa cell survival by participating in mRNA alternative splicing

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.

Breast carcinoma-amplified sequence 2 regulates adult neurogenesis via β-catenin

Background

Breast carcinoma-amplified sequence 2 (BCAS2) regulates β-catenin gene splicing. The conditional knockout of BCAS2 expression in the forebrain (BCAS2 cKO) of mice confers impaired learning and memory along with decreased β-catenin expression. Because β-catenin reportedly regulates adult neurogenesis, we wondered whether BCAS2 could regulate adult neurogenesis via β-catenin.

Methods

BCAS2-regulating neurogenesis was investigated by characterizing BCAS2 cKO mice. Also, lentivirus-shBCAS2 was intracranially injected into the hippocampus of wild-type mice to knock down BCAS2 expression. We evaluated the rescue effects of BCAS2 cKO by intracranial injection of adeno-associated virus encoding BCAS2 (AAV-DJ8-BCAS2) and AAV-β-catenin gene therapy.

Results

To show that BCAS2-regulating adult neurogenesis via β-catenin, first, BCAS2 cKO mice showed low SRY-box 2-positive (Sox2⁺) neural stem cell proliferation and doublecortin-positive (DCX⁺) immature neurons. Second, stereotaxic intracranial injection of lentivirus-shBCAS2 knocked down BCAS2 in the hippocampus of wild-type mice, and we confirmed the BCAS2 regulation of adult neurogenesis via β-catenin. Third, AAV-DJ8-BCAS2 gene therapy in BCAS2 cKO mice reversed the low proliferation of Sox2⁺ neural stem cells and the decreased number of DCX⁺ immature neurons with increased β-catenin expression. Moreover, AAV-β-catenin gene therapy restored neuron stem cell proliferation and immature neuron differentiation, which further supports BCAS2-regulating adult neurogenesis via β-catenin. In addition, cells targeted by AAV-DJ8 injection into the hippocampus included Sox2 and DCX immature neurons, interneurons, and astrocytes. BCAS2 may regulate adult neurogenesis by targeting Sox2⁺ and DCX⁺ immature neurons for autocrine effects and interneurons or astrocytes for paracrine effects.

Conclusions

BCAS2 can regulate adult neurogenesis in mice via β-catenin.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02837-9.

BCAS2 is involved in alternative splicing and mouse oocyte development

Alternative splicing (AS) is an important mechanism to regulate organogenesis and fertility. Breast carcinoma amplified sequence 2 (BCAS2) is one of the core components of the PRP19 complex, a multiple function complex including splicing, and it is involved in the initiation of meiosis through regulating AS in male mice. However, the role of BCAS2 in mouse oogenesis remains largely unknown. In this study, we found that BCAS2 was highly expressed in the oocytes of primordial follicles. Vasa-Cre-mediated deletion of Bcas2 caused poor oocyte quality, abnormal oogenesis and follicular development. The deletion of Bcas2 in mouse oocytes caused alteration in 991 AS events that corresponded to 706 genes, including Pabpc1l, Nobox, Zfp207, Mybl2, Prc1, and Spc25, which were associated with oogenesis and spindle assembly. Moreover, the disruption of BCAS2 led to degradation of PRP19 core proteins in mouse oocytes. These results suggested that BCAS2 was involved in the AS of functional genes through PRP19 complex during mouse oocyte development.

Splicing regulation in hematopoiesis

PURPOSE OF REVIEW

Splicing mutations are among the most recurrent genetic perturbations in hematological malignancies, highlighting an important impact of splicing regulation in hematopoietic development. However, compared to our understanding of splicing factor mutations in hematological malignancies, studies of splicing components and alternative splicing in normal hematopoiesis have been less well investigated. Here, we outline the most recent findings on splicing regulation in normal hematopoiesis and discuss the important questions in the field.

RECENT FINDINGS

Recent studies have highlighted the critical role of splicing regulation in hematopoiesis, including characterization of splicing components in normal hematopoiesis, investigation of transcriptional alterations on splicing, and identification of stage-specific alternative splicing events during hematopoietic development.

SUMMARY

These interesting findings provide insights on hematopoietic regulation at a co-transcriptional level. More high-throughput RNA ribonucleic acid (RNA) sequencing and functional genomic screens are needed to advance our knowledge of critical alternative splicing patterns in shaping hematopoiesis.

BCAS2, a protein enriched in advanced prostate cancer, interacts with NBS1 to enhance DNA double-strand break repair

Background

Breast cancer amplified sequence 2 (BCAS2) plays crucial roles in pre-mRNA splicing and androgen receptor transcription. Previous studies suggested that BCAS2 is involved in double-strand breaks (DSB); therefore, we aimed to characterise its mechanism and role in prostate cancer (PCa).

Methods

Western blotting and immunofluorescence microscopy were used to assay the roles of BCAS2 in the DSBs of PCa cells and apoptosis in Drosophila, respectively. The effect of BCAS2 dosage on non-homologous end joining (NHEJ) and homologous recombination (HR) were assayed by precise end-joining assay and flow cytometry, respectively. Glutathione-S-transferase pulldown and co-immunoprecipitation assays were used to determine whether and how BCAS2 interacts with NBS1. The expression of BCAS2 and other proteins in human PCa was determined by immunohistochemistry.

Results

BCAS2 helped repair radiation-induced DSBs efficiently in both human PCa cells and Drosophila. BCAS2 enhanced both NHEJ and HR, possibly by interacting with NBS1, which involved the BCAS2 N-terminus as well as both the NBS1 N- and C-termini. The overexpression of BCAS2 was significantly associated with higher Gleason and pathology grades and shorter survival in patients with PCa.

Conclusion

BCAS2 promotes two DSB repair pathways by interacting with NBS1, and it may affect PCa progression.

BCAS2 is essential for hematopoietic stem and progenitor cell maintenance during zebrafish embryogenesis

Hematopoietic stem and progenitor cells (HSPCs) originate from the hemogenic endothelium via the endothelial-to-hematopoietic transition, are self-renewing, and replenish all lineages of blood cells throughout life. BCAS2 (breast carcinoma amplified sequence 2) is a component of the spliceosome and is involved in multiple biological processes. However, its role in hematopoiesis remains unknown. We established a bcas2 knockout zebrafish model by using transcription activator-like effector nucleases. The bcas2 ^-/- zebrafish showed severe impairment of HSPCs and their derivatives during definitive hematopoiesis. We also observed significant signs of HSPC apoptosis in the caudal hematopoietic tissue of bcas2 ^-/- zebrafish, which may be rescued by suppression of p53. Furthermore, we show that the bcas2 deletion induces an abnormal alternative splicing of Mdm4 that predisposes cells to undergo p53-mediated apoptosis, which provides a mechanistic explanation of the deficiency observed in HSPCs. Our findings revealed a novel and vital role for BCAS2 during HSPC maintenance in zebrafish.

BCAS2 is involved in alternative mRNA splicing in spermatogonia and the transition to meiosis

Breast cancer amplified sequence 2 (BCAS2) is involved in multiple biological processes, including pre-mRNA splicing. However, the physiological roles of BCAS2 are still largely unclear. Here we report that BCAS2 is specifically enriched in spermatogonia of mouse testes. Conditional disruption of Bcas2 in male germ cells impairs spermatogenesis and leads to male mouse infertility. Although the spermatogonia appear grossly normal, spermatocytes in meiosis prophase I and meiosis events (recombination and synapsis) are rarely observed in the BCAS2-depleted testis. In BCAS2 null testis, 245 genes are altered in alternative splicing forms; at least three spermatogenesis-related genes (Dazl, Ehmt2 and Hmga1) can be verified. In addition, disruption of Bcas2 results in a significant decrease of the full-length form and an increase of the short form (lacking exon 8) of DAZL protein. Altogether, our results suggest that BCAS2 regulates alternative splicing in spermatogonia and the transition to meiosis initiation, and male fertility.

Breast cancer amplified sequence 2 (BCAS2) is involved in pre-mRNA splicing but its physiological role is unclear. Here, the authors find BCAS2 enriched in mice spermatogonia in the testes, and BCAS2 deletion in germ cells alters alternative splicing of spermatogenesis-related genes, causing male infertility.

Conditional Knockout of Breast Carcinoma Amplified Sequence 2 (BCAS2) in Mouse Forebrain Causes Dendritic Malformation via β-catenin

Breast carcinoma amplified sequence 2 (BCAS2) is a core component of the hPrP19 complex that controls RNA splicing. Here, we performed an exon array assay and showed that β-catenin is a target of BCAS2 splicing regulation. The regulation of dendrite growth and morphology by β-catenin is well documented. Therefore, we generated conditional knockout (cKO) mice to eliminate the BCAS2 expression in the forebrain to investigate the role of BCAS2 in dendrite growth. BCAS2 cKO mice showed a microcephaly-like phenotype with a reduced volume in the dentate gyrus (DG) and low levels of learning and memory, as evaluated using Morris water maze analysis and passive avoidance, respectively. Golgi staining revealed shorter dendrites, less dendritic complexity and decreased spine density in the DG of BCAS2 cKO mice. Moreover, the cKO mice displayed a short dendrite length in newborn neurons labeled by DCX, a marker of immature neurons, and BrdU incorporation. To further examine the mechanism underlying BCAS2-mediated dendritic malformation, we overexpressed β-catenin in BCAS2-depleted primary neurons and found that the dendritic growth was restored. In summary, BCAS2 is an upstream regulator of β-catenin gene expression and plays a role in dendrite growth at least partly through β-catenin.