Identification of Novel Variants in Cleft Palate-Associated Genes in Brazilian Patients With Non-syndromic Cleft Palate Only

Unbiased transcriptome analysis of human cleft palate reveals evolutionally conserved molecular signatures of development: experimental study

BACKGROUND

The development of the secondary palate, an essential process for hard palate formation, involves intricate cellular processes. Here, the authors examined the expression patterns of palatal fusion-associated genes in postdevelopmental human palatal tissues.

METHODS

Mucosal samples collected from the anterior fused (control; n =5) and posterior unfused regions (study; n =5) of cleft palate patients were subjected to RNA sequencing. Gene Set Enrichment Analysis (GSEA) was conducted to identify consistent changes in molecular signaling pathways using hallmark (h) gene set collections from the Molecular Signature Database v7.4. The results of RNA sequencing were validated by epithelial-mesenchymal transition (EMT) assays with suppression of target genes, including lrp6, shh, Tgfβ-3 (Bioneer), and negative control siRNA in a human fibroblast cell line (hs68).

RESULTS

Transcriptome profiling of the cleft mucosa demonstrated that the fully fused anterior mucosa exhibited globally upregulated EMT, Wnt β-catenin, Hedgehog, and TGF-β signaling pathways in gene set enrichment. This strongly indicates the evolutionary conserved similarities in pathways implicated in palatogenesis, as previously shown in murine models. In EMT assays with suppression of Lrp6, Shh, and TGF-β3 in human fibroblast cell lines, suppression of Lrp6 exhibited consistent suppression effects on EMT markers. This indicates a closer association with EMT compared to the other two signals.

CONCLUSION

Our study highlights evolutionarily conserved molecular signatures and provides insights into the importance of the EMT pathway in palatal fusion in humans. Furthermore, intraindividual comparative analysis showed the spatial regulation of gene expression within the same organism. Further research and animal models are needed to explore the complexities of EMT-related palatal fusion.

Identification of Novel Risk Variants of Non-Syndromic Cleft Palate by Targeted Gene Panel Sequencing

Non-syndromic cleft palate (ns-CP) has a genetically heterogeneous aetiology. Numerous studies have suggested a crucial role of rare coding variants in characterizing the unrevealed component of genetic variation in ns-CP called the "missing heritability". Therefore, this study aimed to detect low-frequency variants that are implicated in ns-CP aetiology in the Polish population. For this purpose, coding regions of 423 genes associated with orofacial cleft anomalies and/or involved with facial development were screened in 38 ns-CP patients using the next-generation sequencing technology. After multistage selection and prioritisation, eight novel and four known rare variants that may influence an individual's risk of ns-CP were identified. Among detected alternations, seven were located in novel candidate genes for ns-CP, including COL17A1 (c.2435-1G>A), DLG1 (c.1586G>C, p.Glu562Asp), NHS (c.568G>C, p.Val190Leu-de novo variant), NOTCH2 (c.1997A>G, p.Tyr666Cys), TBX18 (c.647A>T, p.His225Leu), VAX1 (c.400G>A, p.Ala134Thr) and WNT5B (c.716G>T, p.Arg239Leu). The remaining risk variants were identified within genes previously linked to ns-CP, confirming their contribution to this anomaly. This list included ARHGAP29 (c.1706G>A, p.Arg569Gln), FLNB (c.3605A>G, Tyr1202Cys), IRF6 (224A>G, p.Asp75Gly-de novo variant), LRP6 (c.481C>A, p.Pro161Thr) and TP63 (c.353A>T, p.Asn118Ile). In summary, this study provides further insights into the genetic components contributing to ns-CP aetiology and identifies novel susceptibility genes for this craniofacial anomaly.

Modifiable Risk Factors of Non-Syndromic Orofacial Clefts: A Systematic Review

OFCs (orofacial clefts) are among the most frequent congenital defects, but their etiology has yet to be clarified. OFCs affect different structures and functions with social, psychological and economic implications in children and their families. Identifying modifiable risk factors is mandatory to prevent the occurrence of non-syndromic OFCs (NSOFCs). PubMed, Cochrane Library, Scopus and Web of Science were searched from 1 January 2012 to 25 May 2022 and a total of 7668 publications were identified. Studies focusing on the risk factors of NSOFCs were selected, leading to 62 case-control and randomized clinical trials. Risk factors were categorized into non-modifiable and modifiable. The first group includes genetic polymorphisms, gender of the newborn, ethnicity, and familiarity. Within the second group, risk factors that can only be modified before conception (consanguinity, parental age at conception, socio-economical and educational level, area of residency and climate), and risk factors modifiable before and after conception (weight, nutritional state, acute and chronic diseases, psychophysical stress, licit and illicit drugs, alcohol, smoke, pollutants and contaminants) have been distinguished. This study provides a wide overview of the risk factors of NSOFCs, focusing on modifiable ones, to suggest new perspectives in education, prevention, medical interventions and clinical research.

Identification of novel susceptibility genes for non-syndromic cleft lip with or without cleft palate using NGS-based multigene panel testing

For non-syndromic cleft lip with or without cleft palate (ns-CL/P), the proportion of heritability explained by the known risk loci is estimated to be about 30% and is captured mainly by common variants identified in genome-wide association studies. To contribute to the explanation of the "missing heritability" problem for orofacial clefts, a candidate gene approach was taken to investigate the potential role of rare and private variants in the ns-CL/P risk. Using the next-generation sequencing technology, the coding sequence of a set of 423 candidate genes was analysed in 135 patients from the Polish population. After stringent multistage filtering, 37 rare coding and splicing variants of 28 genes were identified. 35% of these genetic alternations that may play a role of genetic modifiers influencing an individual's risk were detected in genes not previously associated with the ns-CL/P susceptibility, including COL11A1, COL17A1, DLX1, EFTUD2, FGF4, FGF8, FLNB, JAG1, NOTCH2, SHH, WNT5A and WNT9A. Significant enrichment of rare alleles in ns-CL/P patients compared with controls was also demonstrated for ARHGAP29, CHD7, COL17A1, FGF12, GAD1 and SATB2. In addition, analysis of panoramic radiographs of patients with identified predisposing variants may support the hypothesis of a common genetic link between orofacial clefts and dental abnormalities. In conclusion, our study has confirmed that rare coding variants might contribute to the genetic architecture of ns-CL/P. Since only single predisposing variants were identified in novel cleft susceptibility genes, future research will be required to confirm and fully understand their role in the aetiology of ns-CL/P.

Genetic and epigenetic studies in non-syndromic oral clefts

The etiology of non-syndromic oral clefts (NSOFC) is complex with genetics, genomics, epigenetics, and stochastics factors playing a role. Several approaches have been applied to understand the etiology of non-syndromic oral clefts. These include linkage, candidate gene association studies, genome-wide association studies, whole-genome sequencing, copy number variations, and epigenetics. In this review, we shared these approaches, genes, and loci reported in some studies.

Association between PTCH1 and RAD54B Single-Nucleotide Polymorphisms and Non-syndromic Orofacial Clefts in the Northeast Population of Iran

Background

Non-Syndromic Cleft Lip with or without cleft Palate (NSCL/P) is a common developmental disorder of the head and neck with a multifactorial etiology. The current study aimed to evaluate the potential association of PTCH1 (rs10512248) and RAD54B (rs12681366) polymorphisms with NSCL/P in the Northeast Iranian population.

Methods

In the present study, blood samples were taken from 122 subjects with NSCL/P and 161 healthy controls. Polymerase Chain Reaction (PCR) followed by Restriction Fragment Length Polymorphism (RFLP) were used to conduct genotyping of single-nucleotide polymorphisms.

Results

Although differences were observed between cases and controls in rs10512248 and rs12681366, our data did not support a significant association of these polymorphisms with NSCL/P in our population.

Conclusion

Our findings suggest that polymorphisms of rs10512248 and rs12681366 may not be potential risk factors for NSCL/P in the Northeast Iranian population due to the multifactorial and multiethnicity characteristics of some genes.