The Fam50a positively regulates ameloblast differentiation via interacting with Runx2

Upregulation of FAM50A promotes cancer development

FAM50A encodes a nuclear protein involved in mRNA processing; however, its role in cancer development remains unclear. Herein, we conducted an integrative pan-cancer analysis using The Cancer Genome Atlas, Genotype-Tissue Expression, and the Clinical Proteomic Tumor Analysis Consortium databases. Based on the gene expression data from TCGA and GTEx databases, we compared FAM50A mRNA levels in 33 types of human cancer tissues to those in corresponding normal tissues and found that FAM50A mRNA level was upregulated in 20 of the 33 types of common cancer tissues. Then, we compared the DNA methylation status of the FAM50A promoter in tumor tissues to that in corresponding normal tissues. FAM50A upregulation was accompanied by promoter hypomethylation in 8 of the 20 types of tumor tissues, suggesting that promoter hypomethylation contributes to the upregulation of FAM50A in these cancer tissues. Elevated FAM50A expression in 10 types of cancer tissues was associated with poor prognosis in patients with cancer. FAM50A expression was positively correlated with CD4+ T-lymphocyte and dendritic cell infiltration in cancer tissues but was negatively correlated with CD8+ T-cell infiltration in cancer tissues. FAM50A knockdown caused DNA damage, induced interferon beta and interleukin-6 expression, and repressed the proliferation, invasion, and migration of cancer cells. Our findings indicate that FAM50A might be useful in cancer detection, reveal insights into its role in cancer development, and may contribute to the development of cancer diagnostics and treatments.

Cell-cycle dependent nuclear gene delivery enhances the effects of E-cadherin against tumor invasion and metastasis

Gene delivery is the process by which foreign DNA is transferred to host cells, released from intracellular vesicles, and transported to the nuclei for transcription. This process is frequently inefficient and difficult to control spatiotemporally. We developed a gene delivery strategy that uses ultrasound to directly deliver plasmid DNA into nuclei via gas vesicles (GVs)-based intracellular cavitation. pDNA-binding GVs can be taken up by cells and cause intracellular cavitation when exposed to acoustic irradiation and delivering their pDNA payloads into nuclei. Importantly, GVs can remain stable in the cytoplasm in the absence of acoustic irradiation, allowing for temporally controlled nuclear gene delivery. We were able to achieve spatiotemporal control of E-cadherin nuclear gene delivery in this manner, demonstrating its efficacy in tumor invasion and metastasis inhibition. Interestingly, we discovered that nuclear gene delivery of E-cadherin during the G2/M phase of the cell cycle in C6 tumor cells inhibited tumor invasion and metastasis more effectively than during the G1 and S phases. The gene delivery of E-cadherin at the G2/M phase resulted in significantly lower expression of Fam50a, which reduced Fam50a/Runx2 interaction and led to reduced transactivation of MMP13, an important factor for epithelial-mesenchymal transition, as observed in a molecular mechanism assay. Thus, using remote acoustic control of intracellular cavitation of pDNA-GVs, we developed a high spatiotemporally controllable gene delivery strategy and achieved stronger tumor invasion and metastasis inhibition effects by delivering the E-cadherin gene at the G2/M phase.

FLI1 and FRA1 transcription factors drive the transcriptional regulatory networks characterizing muscle invasive bladder cancer

Bladder cancer is mostly present in the form of urothelium carcinoma, causing over 150,000 deaths each year. Its histopathological classification as muscle invasive (MIBC) and non-muscle invasive (NMIBC) is the most prominent aspect, affecting the prognosis and progression of this disease. In this study, we defined the active regulatory landscape of MIBC and NMIBC cell lines using H3K27ac ChIP-seq and used an integrative approach to combine our findings with existing data. Our analysis revealed FRA1 and FLI1 as two critical transcription factors differentially regulating MIBC regulatory landscape. We show that FRA1 and FLI1 regulate the genes involved in epithelial cell migration and cell junction organization. Knock-down of FRA1 and FLI1 in MIBC revealed the downregulation of several EMT-related genes such as MAP4K4 and FLOT1. Further, ChIP-SICAP performed for FRA1 and FLI1 enabled us to infer chromatin binding partners of these transcription factors and link this information with their target genes. Finally, we show that knock-down of FRA1 and FLI1 result in significant reduction of invasion capacity of MIBC cells towards muscle microenvironment using IC-CHIP assays. Our results collectively highlight the role of these transcription factors in selection and design of targeted options for treatment of MIBC.

Coupling of spliceosome complexity to intron diversity

We determined that over 40 spliceosomal proteins are conserved between many fungal species and humans but were lost during the evolution of S. cerevisiae, an intron-poor yeast with unusually rigid splicing signals. We analyzed null mutations in a subset of these factors, most of which had not been investigated previously, in the intron-rich yeast Cryptococcus neoformans. We found they govern splicing efficiency of introns with divergent spacing between intron elements. Importantly, most of these factors also suppress usage of weak nearby cryptic/alternative splice sites. Among these, orthologs of GPATCH1 and the helicase DHX35 display correlated functional signatures and copurify with each other as well as components of catalytically active spliceosomes, identifying a conserved G patch/helicase pair that promotes splicing fidelity. We propose that a significant fraction of spliceosomal proteins in humans and most eukaryotes are involved in limiting splicing errors, potentially through kinetic proofreading mechanisms, thereby enabling greater intron diversity.

Connexin 43-Mediated Gap Junction Communication Regulates Ameloblast Differentiation via ERK1/2 Phosphorylation

Connexin 43 (Cx43) is an integral membrane protein that forms gap junction channels. These channels mediate intercellular transport and intracellular signaling to regulate organogenesis. The human disease oculodentodigital dysplasia (ODDD) is caused by mutations in Cx43 and is characterized by skeletal, ocular, and dental abnormalities including amelogenesis imperfecta. To clarify the role of Cx43 in amelogenesis, we examined the expression and function of Cx43 in tooth development. Single-cell RNA-seq analysis and immunostaining showed that Cx43 is highly expressed in pre-secretory ameloblasts, differentiated ameloblasts, and odontoblasts. Further, we investigated the pathogenic mechanisms of ODDD by analyzing Cx43-null mice. These mice developed abnormal teeth with multiple dental epithelium layers. The expression of enamel matrix proteins such as ameloblastin (Ambn), which is critical for enamel formation, was significantly reduced in Cx43-null mice. TGF-β1 induces Ambn transcription in dental epithelial cells. The induction of Ambn expression by TGF-β1 depends on the density of the cultured cells. Cell culture at low densities reduces cell–cell contact and reduces the effect of TGF-β1 on Ambn induction. When cell density was high, Ambn expression by TGF-β1 was enhanced. This induction was inhibited by the gap junction inhibitors, oleamide, and 18α-grycyrrhizic acid and was also inhibited in cells expressing Cx43 mutations (R76S and R202H). TGF-β1-mediated phosphorylation and nuclear translocation of ERK1/2, but not Smad2/3, were suppressed by gap junction inhibitors. Cx43 gap junction activity is required for TGF-β1-mediated Runx2 phosphorylation through ERK1/2, which forms complexes with Smad2/3. In addition to its gap junction activity, Cx43 may also function as a Ca²⁺ channel that regulates slow Ca²⁺ influx and ERK1/2 phosphorylation. TGF-β1 transiently increases intracellular calcium levels, and the increase in intracellular calcium over a short period was not related to the expression level of Cx43. However, long-term intracellular calcium elevation was enhanced in cells overexpressing Cx43. Our results suggest that Cx43 regulates intercellular communication through gap junction activity by modulating TGF-β1-mediated ERK signaling and enamel formation.

Mutations in FAM50A suggest that Armfield XLID syndrome is a spliceosomopathy

Intellectual disability (ID) is a heterogeneous clinical entity and includes an excess of males who harbor variants on the X-chromosome (XLID). We report rare FAM50A missense variants in the original Armfield XLID syndrome family localized in Xq28 and four additional unrelated males with overlapping features. Our fam50a knockout (KO) zebrafish model exhibits abnormal neurogenesis and craniofacial patterning, and in vivo complementation assays indicate that the patient-derived variants are hypomorphic. RNA sequencing analysis from fam50a KO zebrafish show dysregulation of the transcriptome, with augmented spliceosome mRNAs and depletion of transcripts involved in neurodevelopment. Zebrafish RNA-seq datasets show a preponderance of 3′ alternative splicing events in fam50a KO, suggesting a role in the spliceosome C complex. These data are supported with transcriptomic signatures from cell lines derived from affected individuals and FAM50A protein-protein interaction data. In sum, Armfield XLID syndrome is a spliceosomopathy associated with aberrant mRNA processing during development.

Armfield X-linked disability (XLID) disorder has previously been linked to a locus in Xq28. Here, the authors report rare missense variants in FAM50A at Xq28, show that FAM50A interacts with the spliceosome, and that mis-splicing is enriched in knockout zebrafish suggesting it is a spliceosomopathy.

Regulatory mechanisms of jaw bone and tooth development

Jaw bones and teeth originate from the first pharyngeal arch and develop in closely related ways. Reciprocal epithelial-mesenchymal interactions are required for the early patterning and morphogenesis of both tissues. Here we review the cellular contribution during the development of the jaw bones and teeth. We also highlight signaling networks as well as transcription factors mediating tissue-tissue interactions that are essential for jaw bone and tooth development. Finally, we discuss the potential for stem cell mediated regenerative therapies to mitigate disorders and injuries that affect these organs.

Hypoplastic AI with Highly Variable Expressivity Caused by ENAM Mutations

Tooth enamel, the hardest tissue in the human body, is formed after a complex series of interactions between dental epithelial tissue and the underlying ectomesenchyme. Nonsyndromic amelogenesis imperfecta (AI) is a rare genetic disorder affecting tooth enamel without other nonoral symptoms. In this study, we identified 2 novel ENAM mutations in 2 families with hypoplastic AI by whole exome sequencing. Family 1 had a heterozygous splicing donor site mutation in intron 4, NM_031889; c.123+2T>G. Affected individuals had hypoplastic enamel with or without the characteristic horizontal hypoplastic grooves in some teeth. Family 2 had a nonsense mutation in the last exon, c.1842C>G, p.(Tyr614*), that was predicted to truncate the protein by 500 amino acids. Participating individuals had at least 1 mutant allele, while the proband had a homozygous mutation. Most interestingly, the clinical phenotype of the individuals harboring the heterozygous mutation varied from a lack of penetrance to a mild hypoplastic enamel defect. We believe that these findings will broaden our understanding of the clinical phenotype of AI caused by ENAM mutations.