Biology subjects

Jerome-Majewska, L. A.

Publications and source records attributed to Jerome-Majewska, L. A..

8 recordsLinked to original sources

bioRxiv2026

Developmental pleiotropy revealed by mosaic heterozygous Snrpb deletion underlies CCMS-like axial skeletal defects

Cerebro-Costo-Mandibular Syndrome (CCMS) is a rare congenital disorder due to pathogenic variants in the core spliceosomal gene SNRPB. Affected individuals present with axial skeletal abnormalities, including cleft palate, micrognathia, posterior rib gaps, and a bell-shaped thorax. The molecular basis of these axial defects remains poorly understood, limiting the development of targeted interventions. To study the temporal and molecular requirements of SNRPB during axial development, we generated a mouse model of CCMS using an inducible Cre-lox system to conditionally delete Snrpb. Mosaic deletion of exons 2-3 of Snrpb after gastrulation resulted in the full spectrum of CCMS-like abnormalities, including micrognathia, posterior rib gaps and a reduced thoracic cavity. Despite normal somite morphology and patterning, transcriptomic analysis of E9.5 mutant somites revealed upregulation of p53 pathway genes and mis-expression of retinoic acid (RA) signaling components, consistent with reduced RA signaling. Alternatively spliced genes in Snrpb mutant somites were associated with post-transcriptional regulation, including chromatin modifiers. To test if RA pathway supplementation can rescue axial defects, we performed dietary RA supplementation; however, this failed to rescue mutant phenotypes, suggesting that p53 activation and chromatin dysregulation additionally contribute to disease pathogenesis. Together, these findings establish the first in vivo model of CCMS-associated axial skeletal abnormalities and indicate that Snrpb dysfunction disrupts the early specification of axial skeletal identity without overtly altering somite patterning.

developmental biology↗

bioRxiv2024

Etiology of Craniofacial and Cardiac Malformations in a Mouse Model of SF3B4-Related Syndromes

Pathogenic variants in SF3B4 are responsible for the acrofacial disorders Nager and Rodriguez Syndrome, also known as SF3B4-related Syndromes, associated with malformations in the head, face, limbs, vertebrae as well as the heart. To uncover the etiology of craniofacial malformations found in SF3B4-related syndromes, mutant mouse lines with homozygous deletion of Sf3b4 in neural crest cells (NCC) were generated. Like in human patients, these embryos had craniofacial and cardiac malformations with variable expressivity and penetrance. The severity and survival of Sf3b4 NCC mutants was modified by the level of Sf3b4 in neighbouring non NCC. RNA sequencing analysis of heads of embryos prior to morphological abnormalities showed significant changes in expression of genes forming the NCC regulatory network, as well as an increase in exon skipping. We identified several key transcription factors and histone modifiers involved in craniofacial and cardiac development with increased exon skipping. Increased exon skipping was also associated with use of a more proximal branch point, as well as an enrichment in thymidine bases in the 50bp around the branch points. We propose that decrease in Sf3b4 causes changes in the expression and splicing of transcripts required for proper craniofacial and cardiac development, leading to abnormalities.

developmental biology↗

bioRxiv2023

Identification of a link between splicing and endoplasmic reticulum proteostasis

The role of general splicing in endoplasmic reticulum (ER)-proteostasis remains poorly understood. Here, we identify SNRPB, a component of the spliceosome, as a novel regulator of export from the ER. Mechanistically, SNRPB regulates the splicing of components of the ER export machinery, including Sec16A, a regulator of ER exit sites. Loss of function of SNRPB is causally linked to cerebro-costo-mandibular syndrome (CCMS), a genetic disease characterized by bone defects. We show that heterozygous deletion of SNRPB in mice resulted in intracellular accumulation of type-1 collagen as well as bone defects reminiscent of CCMS. Silencing SNRPB inhibited osteogenesis in vitro, which could be rescued by overexpression of Sec16A. This indicates that the role of SNRPB in osteogenesis is linked to its effects on ER export. Finally, we show that SNRPB is a target for the unfolded protein response (UPR), which supports a mechanistic link between the spliceosome and ER-proteostasis. Our work highlights SNRPB as a novel node in the proteostasis network, shedding light on CCMS pathophysiology.

cell biology↗

bioRxiv2021

Snrpb, the gene mutated in CCMS, is haploinsufficient and required for proper morphogenesis and splicing

Heterozygous mutations in SNRPB, an essential core component of the five small ribonucleoprotein particles of the spliceosome, are responsible for Cerebrocostomandibular Syndrome (CCMS). We show that Snrpb heterozygous embryos arrest shortly after implantation. Additionally, heterozygous deletion of Snrpb in the developing brain and neural crest cells models craniofacial malformations found in CCMS, and results in death shortly after birth. RNAseq analysis of mutant heads prior to morphological defects revealed increased exon-skipping and intron-retention in association with increased 5 splice site strength. We found increased exon-skipping in negative regulators of the P53-pathway, increased levels of nuclear P53, P53-target genes. However, removing TrP53 in Snrpb heterozygous mutant neural crest cells did not completely rescue craniofacial development. We also found a small but significant increase in exon-skipping of several transcripts required for head and midface development, including Smad2 and Rere. Furthermore, mutant embryos exhibited ectopic or missing expression of Fgf8 and Shh, which are required to coordinate face and brain development. Thus, we propose that mis-splicing of transcripts that regulate P53-activity and craniofacial-specific genes both contribute to craniofacial malformations.

developmental biology↗

bioRxiv2020

Pre-Implantation Alcohol Exposure Induces Lasting Sex-Specific DNA Methylation Programming Errors in the Developing Forebrain

BackgroundPrenatal alcohol exposure is recognized for altering DNA methylation profiles of brain cells during development, and to be part of the molecular basis underpinning Fetal Alcohol Spectrum Disorder (FASD) etiology. However, we have negligible information on the effects of alcohol exposure during pre-implantation, the early embryonic window marked with dynamic DNA methylation reprogramming, and on how this may rewire the brain developmental program. ResultsUsing a pre-clinical in vivo mouse model, we show that a binge-like alcohol exposure during pre-implantation at the 8-cell stage leads to surge in morphological brain defects and adverse developmental outcomes during fetal life. Genome-wide DNA methylation analyses of fetal forebrains uncovered sex-specific alterations, including partial loss of DNA methylation maintenance at imprinting control regions, and abnormal de novo DNA methylation profiles in various biological pathways (e.g., neural/brain development). ConclusionThese findings support that alcohol-induced DNA methylation programming deviations during pre-implantation could contribute to the manifestation of neurodevelopmental phenotypes associated with FASD.

developmental biology↗

bioRxiv2020

Mis-splicing of Mdm2 leads to increased P53-activity and craniofacial defects in a MFDM Eftud2 mutant mouse model

EFTUD2, a GTPase and core component of the splicesome, is mutated in patients with mandibulofacial dysostosis with microcephaly (MFDM). We generated a mutant mouse line with conditional mutation in Eftud2 and used Wnt1-Cre2 to delete it in neural crest cells. Homozygous deletion of Eftud2 leads to neural crest cell death and malformations in the brain and craniofacial region of embryos. RNAseq analysis of embryonic mutant heads revealed a significant increase in exon skipping, in retained introns and enriched levels of Mdm2 transcripts lacking exon 3. Mutants also had increased nuclear P53, higher expression of P53-target genes, and increased cell death. Their craniofacial development was significantly improved when treated with Pifithrin-, an inihibitor of P53. We propose that craniofacial defects caused by mutations of EFTUD2 are a result of mis-splicing of Mdm2 and P53-associated cell death. Hence, drugs that reduce P53 activity may help prevent craniofacial defects associated with spliceosomopathies.

developmental biology↗

bioRxiv2020

Tmed2 regulates Smoothened trafficking and Hedgehog signalling

Hedgehog (HH) signalling plays a key role in embryonic pattering and stem cell differentiation. Compounds that selectively bind Smoothened (SMO) can induce cell death in mouse embryonic stem cells (ESCs). Here we perform a genetic screen in haploid ESCs and discover that SMO inhibits a cell death pathway that resembles dissociation induced death of human ESCs and Anoikis. In mouse ESCs, SMO acts through a G-protein coupled mechanism that is independent of GLI activation. Our screen also identifies the Golgi proteins Tmed2 and Tmed10. We show that TMED2 binds SMO and controls its abundance at the plasma membrane. In neural differentiation and neural tube pattering Tmed2 acts as a repressor of HH signalling strength. We demonstrate that the interaction between SMO and TMED2 is regulated by HH signalling suggesting SMO release form the ER-Golgi is critical for controlling G-protein and GLI mediated functions of mammalian HH signalling.

cell biology↗

bioRxiv2019

Loss of function mutation of mouse Snap29 on a mixed genetic background phenocopy abnormalities found in CEDNIK and 22q11.2 Deletion Syndrome patients

Synaptosomal-associated protein 29 (SNAP29) is a member of the SNARE family of proteins involved in maintenance of various intracellular protein trafficking pathways. SNAP29 maps to the 22q11.2 region and is deleted in 90% of patients with 22q11.2 deletion syndrome (22q11.2DS). However, the contribution of hemizygosity of SNAP29 to developmental abnormalities in 22q11.2DS remains to be determined. Mutations in SNAP29 are responsible for the developmental syndrome called CEDNIK (cerebral dysgenesis, neuropathy, ichthyosis, and keratoderma). On an inbred C57Bl/6J genetic background, only the ichthyotic skin defect associated with CEDNIK was reported. In this study, we show that loss of function mutation of Snap29 on a mixed genetic background not only models skin abnormalities found in CEDNIK, but also phenocopy ophthalmological, neurological, and motor defects found in these patients and a subset of 22q11.2DS patients. Thus, our findings indicate that mouse models of human syndromes should be analyzed on a mixed genetic background. Our work also reveals an unanticipated requirement for Snap29 in male fertility, and support contribution of hemizygosity for SNAP29 to the phenotypic spectrum of abnormalities found in 22q11.2DS patients.

developmental biology↗