Genes Related to Frontonasal Malformations Are Regulated by miR-338-5p, miR-653-5p, and miR-374-5p in O9-1 Cells.

Frontonasal malformations are caused by a failure in the growth of the frontonasal prominence during development. Although genetic studies have identified genes that are crucial for frontonasal development, it remains largely unknown how these genes are regulated during this process. Here, we show that microRNAs, which are short non-coding RNAs capable of targeting their target mRNAs for degradation or silencing their expression, play a crucial role in the regulation of genes related to frontonasal development in mice. Using the Mouse Genome Informatics (MGI) database, we curated a total of 25 mouse genes related to frontonasal malformations, including frontonasal hypoplasia, frontonasal dysplasia, and hypotelorism. MicroRNAs regulating the expression of these genes were predicted through bioinformatic analysis. We then experimentally evaluated the top three candidate miRNAs (miR-338-5p, miR-653-5p, and miR-374c-5p) for their effect on cell proliferation and target gene regulation in O9-1 cells, a neural crest cell line. Overexpression of these miRNAs significantly inhibited cell proliferation, and the genes related to frontonasal malformations (Alx1, Lrp2, and Sirt1 for miR-338-5p; Alx1, Cdc42, Sirt1, and Zic2 for miR-374c-5p; and Fgfr2, Pgap1, Rdh10, Sirt1, and Zic2 for miR-653-5p) were directly regulated by these miRNAs in a dose-dependent manner. Taken together, our results highlight miR-338-5p, miR-653-5p, and miR-374c-5p as pathogenic miRNAs related to the development of frontonasal malformations.

Craniofacial bone anomalies related to cholesterol synthesis defects.

DHCR7 and SC5D are enzymes crucial for cholesterol biosynthesis, and mutations in their genes are associated with developmental disorders, which are characterized by craniofacial deformities. We have recently reported that a loss of either Dhcr7 or Sc5d results in a failure in osteoblast differentiation. However, it remains unclear to what extent a loss of function in either DHCR7 or SC5D affects craniofacial skeletal formation. Here, using micro computed tomography (µCT), we found that the bone phenotype differs in Dhcr7-/- and Sc5d-/- mice in a location-specific fashion. For instance, in Sc5d-/- mice, although craniofacial bones were overall affected, some bone segments, such as the anterior part of the premaxilla, the anterior-posterior length of the frontal bone, and the main body of the mandible, did not present significant differences compared to WT controls. By contrast, in Dhcr7-/- mice, while craniofacial bones were not much affected, the frontal bone was larger in width and volume, and the maxilla and palatine bone were hypoplastic, compared to WT controls. Interestingly the mandible in Dhcr7-/- mice was mainly affected at the condylar region, not the body. Thus, these results help us understand which bones and how greatly they are affected by cholesterol metabolism aberrations in Dhcr7-/- and Sc5d-/- mice.

Single-cell multiomics decodes regulatory programs for mouse secondary palate development.

Perturbations in gene regulation during palatogenesis can lead to cleft palate, which is among the most common congenital birth defects. Here, we perform single-cell multiome sequencing and profile chromatin accessibility and gene expression simultaneously within the same cells (n = 36,154) isolated from mouse secondary palate across embryonic days (E) 12.5, E13.5, E14.0, and E14.5. We construct five trajectories representing continuous differentiation of cranial neural crest-derived multipotent cells into distinct lineages. By linking open chromatin signals to gene expression changes, we characterize the underlying lineage-determining transcription factors. In silico perturbation analysis identifies transcription factors SHOX2 and MEOX2 as important regulators of the development of the anterior and posterior palate, respectively. In conclusion, our study charts epigenetic and transcriptional dynamics in palatogenesis, serving as a valuable resource for further cleft palate research.

Investigating gene functions and single-cell expression profiles of de novo variants in orofacial clefts.

Orofacial clefts (OFCs) are common congenital birth defects with various etiologies, including genetic variants. Online Mendelian Inheritance in Man (OMIM) annotated several hundred genes involving OFCs. Furthermore, several hundreds of de novo variants (DNVs) have been identified from individuals with OFCs. Some DNVs are related to known OFC genes or pathways, but there are still many DNVs whose relevance to OFC development is unknown. To explore novel gene functions and their cellular expression profiles, we focused on DNVs in genes that were not listed in OMIM. We collected 960 DNVs in 853 genes from published studies and curated these genes, based on the DNVs' deleteriousness, into 230 and 23 genes related to cleft lip with or without cleft palate (CL/P) and cleft palate only (CPO), respectively. For comparison, we curated 178 CL/P and 277 CPO genes from OMIM. In CL/P, the pathways enriched in DNV and OMIM genes were significantly overlapped (p = 0.002). Single-cell RNA sequencing (scRNA-seq) analysis of mouse lip development revealed that both gene sets had abundant expression in the ectoderm (DNV genes: adjusted p = 0.032, OMIM genes: adjusted p < 0.0002), while only DNV genes were enriched in the endothelium (adjusted p = 0.032). Although we did not achieve significant findings using CPO gene sets, which was mainly due to the limited number of DNV genes, scRNA-seq analysis implicated various expression patterns among DNV and OMIM genes. Our results suggest that combinatory pathway and scRNA-seq data analyses are helpful for contextualizing genes in OFC development.