NSrp70 is significant for embryonic growth and development, being a crucial factor for gastrulation and mesoderm induction

A milder form of NSRP1-associated neurodevelopmental disorder, caused by a missense variant in the nuclear localization signal

Nuclear Speckle Splicing Regulator Protein 1 (NSRP1) is a splice factor found in nuclear speckles, which are small membrane-free organelles implicated in epigenetic regulation, chromatin organization, DNA repair, and RNA modification. Bi-allelic loss-of-function variants in NSRP1 have recently been identified in patients suffering from a severe neurodevelopmental disorder, presenting with neurodevelopmental delay, epilepsy, microcephaly, hypotonia, and spastic cerebral palsy. Described patients acquired neither independent walking nor speech and often showed anomalies on cerebral MRI. Here we describe the case of a 14-year-old girl with motor and language delay as well as intellectual disability, who presents an ataxic gait but walks without assistance and speaks in short sentences. Whole-genome sequencing revealed the compound heterozygous NSRP1 variants c.114 + 2T > G and c.1595T > A (p.Val532Glu). Functional validation using HEK293T cells transfected with either wild-type or mutated GFP-tagged Nsrp1 suggests that the Val532Glu variant interferes with the function of the nuclear localization signal, and leads to mislocalization of NSRP1 in the cytosol, thus confirming the pathogenicity of the observed variant. This case helps to expand the phenotypic and genetic spectrum associated with pathogenic NSRP1 variants and indicates that this diagnosis should also be suspected in patients with milder phenotypes.

NSrp70 suppresses metastasis in triple-negative breast cancer by modulating Numb/TβR1/EMT axis

Alternative splicing of mRNA precursors allows cancer cells to create different protein isoforms that promote growth and survival. Compared to normal cells, cancer cells frequently exhibit a higher diversity of their transcriptomes. A comprehensive understanding of splicing regulation is required to correct the splicing alterations for the future precision oncology. A quantitative proteomic screen was performed to identify the regulators associated the metastasis in triple-negative breast cancer. Multiple in vitro and in vivo functional analyses were used to study the effects of NSrp70 on breast cancer metastasis. Next, transcriptomic sequencing (RNA-seq) and alternative splicing bioinformatics analysis was applied to screen the potential targets of NSrp70. Moreover, in vitro splicing assays, RNA pull-down, and RNA immunoprecipitation assay were used to confirm the specific binding between NSrp70 and downstream target genes. Furthermore, the prognostic value of NSrp70 was analyzed in a cohort of patients by performing IHC. We uncovered NSrp70 as a novel suppressor of breast cancer metastasis. We discovered that NSrp70 inhibited the skipped exon alternative splicing of NUMB, promoted the degradation of transforming growth factor receptor 1 through lysosome pathway, and regulated TGFβ/SMAD-mediated epithelial-mesenchymal transition phenotype in breast cancer cells. Furthermore, high NSrp70 expression correlated with a better prognosis in breast cancer patients. Our findings revealed that splicing regulator NSrp70 serves as a metastasis suppressor.

Biallelic loss-of-function variants in the splicing regulator NSRP1 cause a severe neurodevelopmental disorder with spastic cerebral palsy and epilepsy

PURPOSE

Alternative splicing plays a critical role in mouse neurodevelopment, regulating neurogenesis, cortical lamination, and synaptogenesis, yet few human neurodevelopmental disorders are known to result from pathogenic variation in splicing regulator genes. Nuclear Speckle Splicing Regulator Protein 1 (NSRP1) is a ubiquitously expressed splicing regulator not known to underlie a Mendelian disorder.

METHODS

Exome sequencing and rare variant family-based genomics was performed as a part of the Baylor-Hopkins Center for Mendelian Genomics Initiative. Additional families were identified via GeneMatcher.

RESULTS

We identified six patients from three unrelated families with homozygous loss-of-function variants in NSRP1. Clinical features include developmental delay, epilepsy, variable microcephaly (Z-scores -0.95 to -5.60), hypotonia, and spastic cerebral palsy. Brain abnormalities included simplified gyral pattern, underopercularization, and/or vermian hypoplasia. Molecular analysis identified three pathogenic NSRP1 predicted loss-of-function variant alleles: c.1359_1362delAAAG (p.Glu455AlafsTer20), c.1272dupG (p.Lys425GlufsTer5), and c.52C>T (p.Gln18Ter). The two frameshift variants result in a premature termination codon in the last exon, and the mutant transcripts are predicted to escape nonsense mediated decay and cause loss of a C-terminal nuclear localization signal required for NSRP1 function.

CONCLUSION

We establish NSRP1 as a gene for a severe autosomal recessive neurodevelopmental disease trait characterized by developmental delay, epilepsy, microcephaly, and spastic cerebral palsy.

Rbm14 maintains the integrity of genomic DNA during early mouse embryogenesis via mediating alternative splicing

OBJECTIVE

In this study, we generated an Rbm14 knockout mouse model to explore its functions during early mouse embryogenesis.

MATERIALS AND METHODS

The Rbm14 knockout mouse model was generated by a combination of clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 and microinjection techniques. The developmental defects of the knockout embryos were characterized by histological analyses. The accumulation of DNA damage in mouse embryonic stem cells (ESCs) was detected by γH2AX staining and comet assay. The altered mRNA splicing of DNA damage response (DDR)-related genes was detected by RNA-Seq analysis and confirmed by semi-quantitative PCR. The interaction of RBM14 with alternative splicing-related genes was detected by immunoprecipitation-mass spectra (IP-MS) and confirmed by co-immunoprecipitation (Co-IP).

RESULTS

Rbm14 knockout in mice results in apoptosis and cell proliferation defects in early post-implantation epiblast cells, leading to gastrulation disruption and embryonic lethality. FACS and immunostaining demonstrate accumulation of DNA damage in Rbm14 knockout ES cells. We also identified altered splicing of DDR-related genes in the knockout mouse ESCs by RNA-Seq, indicating that RBM14-mediated alternative splicing is required for the maintenance of genome integrity during early mouse embryogenesis.

CONCLUSIONS

Our work reveals that Rbm14 plays an essential role in the maintenance of genome integrity during early mouse embryonic development by regulating alternative splicing of DDR-related genes.

RBM14 is indispensable for pluripotency maintenance and mesoderm development of mouse embryonic stem cells

The pluripotency of embryonic stem cells (ESCs) is maintained by core pluripotency transcription factors, cofactors and several signaling pathways. RBM14 is a component of the para-speckle complex, which has been implicated in multiple important biological processes. The role of RBM14 in ESCs and lineage differentiation remains to be elucidated. In the present study, we provided evidence that RBM14 plays important roles in maintaining pluripotency and in the early differentiation of ESCs. RBM14 was demonstrated to be expressed in mouse embryonic stem cells (mESCs) and localized in the nucleus. RBM14 expression was depleted in mESCs using clustered regularly interspaced short palindromic repeats (CRISPR) technology. Our results also showed that RBM14 depletion altered the gene expression profiles of mESCs. In particular, pluripotency-associated genes and genes involved in the Wnt and TGF-β signaling pathways were downregulated in RBM14 knockout mESCs. Furthermore, RBM14 was found to be essential for mesoderm development in vitro and in vivo. The specific effects of RBM14 depletion were verified by conducting a rescue experiment. Our findings demonstrated that RBM14 not only plays an important role in maintaining the pluripotency of mESCs but is also indispensable for mesoderm development.