Genome-wide meta-analyses of nonsyndromic cleft lip with or without cleft palate identify six new risk loci

Targeted Resequencing Identifies Novel MAFB Variants Associated With Nonsyndromic Cleft Lip With or Without Cleft Palate

ObjectivesNonsyndromic cleft lip with or without palate (NSCL/P) is one of the most prevalent congenital orofacial defects. It arises from a combination of genetic and environmental factors. This study aims to identify new risk loci around the musculoaponeurotic fibrosarcoma oncogene family, protein B (MAFB) gene in NSCL/P patients from the Western Han Chinese population.DesignA targeted region sequencing approach was employed to examine the MAFB gene in 159 NSCL/P cases. We conducted both single-variant association and gene-based burden analyses.SettingThe study was conducted in a stomatological hospital.Patients, participantsOne hundred and fifty-nine NSCL/P cases were analyzed.InterventionsBlood samples were collected.Main outcome measuresTo explore the association analysis between variants at MAFB and NSCL/P in Western Han Chinese population.ResultsWe identified a cluster of significant common variants near the 3' end of MAFB. Notably, rs6029223 showed significantly associated with NSCL/P (P = 3.82E-09, odds ration [OR] = 0.29, 95% confidence interval [CI]: 0.18-0.46), nonsyndromic cleft lip and palate (NSCLP) (P = 5.31E-08, OR = 0.25, 95% CI: 0.14-0.44) and nonsyndromic cleft lip only (NSCLO) (P = 1.3E-04, OR = 0.34, 95%CI: 0.19-0.62). In Addition, rs79836852 and rs200392238 were significantly associated with both NSCL/P and NSCLP.ConclusionsOur study revealed that single nucleotide polymorphisms near the 3' end of the MAFB gene are risk factors for NSCL/P and NSCLP in the Western Han Chinese population. Our findings reinforce the notion that MAFB is a susceptibility gene for NSCL/P.

Exome analyses unravel the genetic architecture of Mendelian dominant nonsyndromic orofacial clefts

Nonsyndromic orofacial clefts (NSOFC) represents a prevalent congenital anomalies, the etiology of which likely involves a complex interplay between genetic and environmental factors. To elucidate potential pathogenic variants, exome sequencing (ES) was conducted on 123 Chinese pedigrees demonstrating Mendelian dominant inheritance of NSOFC, including 251 patients and 130 unaffected relatives. This was followed by a standardized process of variant screening and filtering to identify novel variants within established candidate genes associated with clefting phenotypes. The study unveiled rare pathogenic variants in recognized genes with clefting across 101 pedigrees. These genes are implicated in essential biological processes such as primary ciliary function, bone formation and development, cell adhesion, and transcription regulation. Notably, the investigation into random X chromosome inactivation assay posited FLNA and GPC3 as factors contributing to NSOFC's incomplete dominance. Moreover, in vitro functional experiments targeting variants in two ciliary genes, TBC1D32 and SCLT1, elucidated their roles in NSOFC pathogenesis.

Identification of functional non-coding variants associated with orofacial cleft

Oral facial cleft (OFC) is a multifactorial disorder that can present as a cleft lip with or without cleft palate (CL/P) or a cleft palate only. Genome wide association studies (GWAS) of isolated OFC have identified common single nucleotide polymorphisms (SNPs) at the 1q32/ IRF6 locus and many other loci where, like IRF6 , the presumed OFC-relevant gene is expressed in embryonic oral epithelium. To identify the functional subset of SNPs at eight such loci we conducted a massively parallel reporter assay in a cell line derived from fetal oral epithelium, revealing SNPs with allele-specific effects on enhancer activity. We filtered these against chromatin-mark evidence of enhancers in relevant cell types or tissues, and then tested a subset in traditional reporter assays, yielding six candidates for functional SNPs in five loci (1q32/ IRF6 , 3q28/ TP63 , 6p24.3/ TFAP2A , 20q12/ MAFB , and 9q22.33/ FOXE1 ). We further tested two SNPs near IRF6 and one near FOXE1 by engineering the genome of induced pluripotent stem cells, differentiating the cells into embryonic oral epithelium, and measuring expression of IRF6 or FOXE1 and binding of transcription factors; the results strongly supported their candidacy. Conditional analyses of a meta-analysis of GWAS suggest that the two functional SNPs near IRF6 account for the majority of risk for CL/P associated with variation at this locus. This study connects genetic variation associated with orofacial cleft to mechanisms of pathogenesis.

Functional variant at 19q13.3 confers nonsyndromic cleft palate susceptibility by regulating HIF3A

This study investigates the genetic factors associated with nonsyndromic cleft palate only (NSCPO) through a two-stage genome-wide association study (GWAS) and functional experiments. A total of 311 NSCPO cases and 1,136 controls were included, and we identified rs3826795 in HIF3A significantly associated with NSCPO risk (p = 4.27E-09). Functional assays showed that the A allele of rs3826795 reduced VEZF1 binding to the HIF3A promoter, thereby enhancing HIF3A expression. Additionally, we demonstrated that HIF3A significantly influenced cellular processes, including apoptosis, proliferation, and migration, in both in vitro and in vivo models. Pathway enrichment analysis indicated that HIF3A suppressed the GABAergic synapse pathway, which plays a crucial role in embryonic development. These findings provide valuable insights into the genetic mechanisms underlying NSCPO susceptibility and suggest potential targets for future therapeutic interventions.

Genetic-epigenetic interactions (meQTLs) in orofacial clefts etiology

Objectives

Nonsyndromic orofacial clefts (OFCs) etiology involves multiple genetic and environmental factors with over 60 identified risk loci; however, they account for only a minority of the estimated risk. Epigenetic factors such as differential DNA methylation (DNAm) are also associated with OFCs risk and can alter risk for different cleft types and modify OFCs penetrance. DNAm is a covalent addition of a methyl (CH3) group to the nucleotide cytosine that can lead to changes in expression of the targeted gene. DNAm can be affected by environmental influences and genetic variation via methylation quantitative loci (meQTLs). We hypothesize that aberrant DNAm and the resulting alterations in gene expression play a key role in the etiology of OFCs, and that certain common genetic variants that affect OFCs risk do so by influencing DNAm.

Methods

We used genotype from 10 cleft-associated SNPs and genome-wide DNA methylation data (Illumina 450K array) for 409 cases with OFCs and 456 controls and identified 23 cleft-associated meQTLs. We then used an independent cohort of 362 cleft-discordant sib pairs for replication. We used methylation-specific qPCR to measure methylation levels of each CpG site and combined genotypic and methylation data for an interaction analysis of each SNP-CpG pair using the R package MatrixeQTL in a linear model. We also performed a Paired T-test to analyze differences in DNA methylation between each member of the sibling pairs.

Results

We replicated 9 meQTLs, showing interactions between rs13041247 (MAFB) - cg18347630 (PLCG1) (P=0.04); rs227731 (NOG) - cg08592707 (PPM1E) (P=0.01); rs227731 (NOG) - cg10303698 (CUEDC1) (P=0.001); rs3758249 (FOXE1) - cg20308679 (FRZB) (P=0.04); rs8001641 (SPRY2) - cg19191560 (LGR4) (P=0.04); rs987525(8q24) - cg16561172(MYC) (P=0.00000963); rs7590268(THADA) - cg06873343 (TTYH3) (P=0.04); rs7078160 (VAX1) - cg09487139 (P=0.05); rs560426 (ABCA4/ARHGAP29) - cg25196715 (ABCA4/ARHGAP29) (P=0,03). Paired T-test showed significant differences for cg06873343 (TTYH3) (P=0.04); cg17103269 (LPIN3) (P=0.002), and cg19191560 (LGR4) (P=0.05).

Conclusions

Our results confirm previous evidence that some of the common non-coding variants detected through GWAS studies can influence the risk of OFCs via epigenetic mechanisms, such as DNAm, which can ultimately affect and regulate gene expression. Given the large prevalence of non-coding SNPs in most OFCs genome wide association studies, our findings can potentially address major knowledge gaps, like missing heritability, reduced penetrance, and variable expressivity associated with OFCs phenotypes.

Gene expression patterns of the developing human face at single cell resolution reveal cell type contributions to normal facial variation and disease risk

Craniofacial development gives rise to the complex structures of the face and involves the interplay of diverse cell types. Despite its importance, our understanding of human-specific craniofacial developmental mechanisms and their genetic underpinnings remains limited. Here, we present a comprehensive single-nucleus RNA sequencing (snRNA-seq) atlas of human craniofacial development from craniofacial tissues of 24 embryos that span six key time points during the embryonic period (4-8 post-conception weeks). This resource resolves the transcriptional dynamics of seven major cell types and uncovers distinct major cell types, including muscle progenitors and cranial neural crest cells (CNCCs), as well as dozens of subtypes of ectoderm and mesenchyme. Comparative analyses reveal substantial conservation of major cell types, alongside human biased differences in gene expression programs. CNCCs, which play a crucial role in craniofacial morphogenesis, exhibit the lowest marker gene conservation, underscoring their evolutionary plasticity. Spatial transcriptomics further localizes cell populations, providing a detailed view of their developmental roles and anatomical context. We also link these developmental processes to genetic variation, identifying cell type-specific enrichments for common variants associated with facial morphology and rare variants linked to orofacial clefts. Intriguingly, Neanderthal-introgressed sequences are enriched near genes with biased expression in cartilage and specialized ectodermal subtypes, suggesting their contribution to modern human craniofacial features. This atlas offers unprecedented insights into the cellular and genetic mechanisms shaping the human face, highlighting conserved and distinctly human aspects of craniofacial biology. Our findings illuminate the developmental origins of craniofacial disorders, the genetic basis of facial variation, and the evolutionary legacy of ancient hominins. This work provides a foundational resource for exploring craniofacial biology, with implications for developmental genetics, evolutionary biology, and clinical research into congenital anomalies.

Multi-ancestry Genome Wide Association Study Meta-analysis of Non-syndromic Orofacial Clefts

Non-syndromic orofacial clefts (NSOC) are common craniofacial birth defects, and result from both genetic and environmental factors. NSOC include three major sub-phenotypes: non-syndromic cleft lip with palate (NSCLP), non-syndromic cleft lip only (NSCLO) and non-syndromic cleft palate only (NSCPO), NSCLP and NSCLO are also sometimes grouped as non-syndromic cleft lip with or without cleft palate (NSCL/P) based on epidemiology. Currently known loci only explain a limited proportion of the heritability of NSOC. Further, differences in genetic susceptibility among the sub-phenotypes are poorly characterized. We performed a multi-ancestry GWAS meta-analysis on 44,094 individuals (9,381 cases, 28,510 controls, 2042 case-parent trios and 18 multiplex pedigrees) of East Asian, European, Latin and South American, and African ancestry for both NSOC and subtypes. We identified 50 loci, including 11 novel loci: four loci ( CALD1 , SHH , NRG1 and LINC00320 ) associated with both NSOC and NSCL/P, two loci ( NTRK1 and RUNX1 ) only associated with NSOC, four loci ( HMGCR , PRICKLE1 , SOX9 and MYH9 ) only associated with NSCL/P and one locus ( ALX1 ) specifically associated with NSCLO. Five of the novel loci are located in regions containing genes associated with syndromic orofacial clefts ( SHH , NTRK1, CALD1, ALX1 and SOX9 ); seven of the novel loci are located in regions containing genes-implicated in craniofacial development ( HMGCR, SHH, PRICKLE1, ALX1, SOX9, RUNX1, MYH9 ). Genetic correlation and colocalization analyses revealed an overlap between signals associated with NSCLO, NSCPO and NSCLP, but there were also notable differences, emphasizing the complexity of common and distinct genetic processes affecting lip and palate development.

Combining genetic and single-cell expression data reveals cell types and novel candidate genes for orofacial clefting

Non-syndromic cleft lip with/without cleft palate (nsCL/P) is one of the most common birth defects and has a multifactorial etiology. To date, over 45 loci harboring common risk variants have been identified. However, the effector genes at these loci, and the cell types that are affected by risk alleles, remain largely unknown. To address this, we combined genetic data from an nsCL/P genome-wide association study (GWAS) with single-cell RNA sequencing data obtained from the heads of unaffected human embryos. Using the recently developed single-cell disease relevance score (scDRS) approach, we identified two major cell types involved in nsCL/P development, namely the epithelium and the HAND2+ pharyngeal arches (PA). Combining scDRS with co-expression networks and differential gene expression analysis, we prioritized nsCL/P candidate genes, some of which were additionally supported by GWAS data (e.g., CTNND1, PRTG, RPL35A, RAB11FIP1, KRT19). Our results suggest that specific epithelial and PA sub-cell types are involved in nsCL/P development, and harbor a substantial fraction of the genetic risk for nsCL/P.

Integrated Analysis of the Association Between Variants at PAX7 and NSCL/P in the Han Population

OBJECTIVE

Paired box 7 (PAX7) has been considered as a candidate gene for non-syndromic cleft lip with or without palate (NSCL/P). However, there is no research for the XXX, and previous studies concentrated on limited variants. This study aimed to conduct sufficiently dense and powerful scans of variants at PAX7 and explored the roles of variants at PAX7 in NSCL/P among the XXX.

DESIGN

Targeted region sequencing was performed to thoroughly screen variations, followed by a two-phase association analysis. 159 NSCL/P cases and 542 controls were analyzed in phase 1. Then in phase 2, the validation study was performed using 1626 cases and 2255 controls. We also explored the roles of variants at PAX7 gene in NSCL/P subtypes. Additionally, indirect associations were found by calculating LD and haplotypes.

SETTING

The study was conducted in XXX.

PATIENTS, PARTICIPANTS

159 NSCL/P cases and 542 controls were analyzed in phase 1. Then in phase 2, the validation study was performed using 1626 cases and 2255 controls.

INTERVENTIONS

Blood samples were collected.

MAIN OUTCOME MEASURES

To explore the association analysis between variants at PAX7 and NSCL/P in XXX.

RESULTS

The results showed that rs2236810, rs114882979 and rs2236804 were significantly associated with NSCL/P, which were predicted to have regulatory functions. Besides, variants at PAX7 function differently in the NSCL/P subtypes. We also discovered a PAX7 missense variant, NM_001135254 p.A369 V (NM_002584.2:c.1106C > T).

CONCLUSIONS

In summary, we confirmed 3 SNPs at PAX7 were significantly associated with NSCL/P in XXX and identified a missense variant, NM_001135254 p.A369 V (NM_002584.2:c.1106C > T).

DeepFace: Deep-learning-based framework to contextualize orofacial-cleft-related variants during human embryonic craniofacial development

Orofacial clefts (OFCs) are among the most common human congenital birth defects. Previous multiethnic studies have identified dozens of associated loci for both cleft lip with or without cleft palate (CL/P) and cleft palate alone (CP). Although several nearby genes have been highlighted, the "casual" variants are largely unknown. Here, we developed DeepFace, a convolutional neural network model, to assess the functional impact of variants by SNP activity difference (SAD) scores. The DeepFace model is trained with 204 epigenomic assays from crucial human embryonic craniofacial developmental stages of post-conception week (pcw) 4 to pcw 10. The Pearson correlation coefficient between the predicted and actual values for 12 epigenetic features achieved a median range of 0.50-0.83. Specifically, our model revealed that SNPs significantly associated with OFCs tended to exhibit higher SAD scores across various variant categories compared to less related groups, indicating a context-specific impact of OFC-related SNPs. Notably, we identified six SNPs with a significant linear relationship to SAD scores throughout developmental progression, suggesting that these SNPs could play a temporal regulatory role. Furthermore, our cell-type specificity analysis pinpointed the trophoblast cell as having the highest enrichment of risk signals associated with OFCs. Overall, DeepFace can harness distal regulatory signals from extensive epigenomic assays, offering new perspectives for prioritizing OFC variants using contextualized functional genomic features. We expect DeepFace to be instrumental in accessing and predicting the regulatory roles of variants associated with OFCs, and the model can be extended to study other complex diseases or traits.

invdup(8)(8q24.13q24.3)-A Complex Alteration and Its Clinical Consequences

Structural variation is a source of genetic variation that, in some cases, may trigger pathogenicity. Here, we describe two cases, a mother and son, with the same partial inverted duplication of the long arm of chromosome 8 [invdup(8)(q24.21q24.21)] of 17.18 Mb, showing different clinical manifestations: microcephaly, dorsal hypertrichosis, seizures and neuropsychomotor development delay in the child, and a cleft lip/palate, down-slanted palpebral fissures and learning disabilities in the mother. The deleterious outcome, in general, is reflected by the gain or loss of genetic material. However, discrepancies among the clinical manifestations raise some concerns about the genomic configuration within the chromosome and other genetic modifiers. With that in mind, we also performed a literature review of research published in the last 20 years about the duplication of the same, or close, chromosome region, seeking the elucidation of at least some relevant clinical features.

High incidence and geographic distribution of cleft palate cases in Finland are associated with a regulatory variant in IRF6

In Finland the frequency of isolated cleft palate (CP) is higher than that of isolated cleft lip with or without cleft palate (CL/P). This trend contrasts to that in other European countries but its genetic underpinnings are unknown. We performed a genome-wide association study for orofacial clefts, which include CL/P and CP, in the Finnish population. We identified rs570516915, a single nucleotide polymorphism that is highly enriched in Finns and Estonians, as being strongly associated with CP ( P = 5.25 × 10 -34 , OR = 8.65, 95% CI 6.11-12.25), but not with CL/P ( P = 7.2 × 10 -5 ), with genome-wide significance. The risk allele frequency of rs570516915 parallels the regional variation of CP prevalence in Finland, and the association was replicated in independent cohorts of CP cases from Finland ( P = 8.82 × 10 -28 ) and Estonia ( P = 1.25 × 10 -5 ). The risk allele of rs570516915 disrupts a conserved binding site for the transcription factor IRF6 within a previously characterized enhancer upstream of the IRF6 gene. Through reporter assay experiments we found that the risk allele of rs570516915 diminishes the enhancer activity. Oral epithelial cells derived from CRISPR-Cas9 edited induced pluripotent stem cells demonstrate that the CP-associated allele of rs570516915 concomitantly decreases the binding of IRF6 and the expression level of IRF6 , suggesting impaired IRF6 autoregulation as a molecular mechanism underlying the risk for CP.

Custom Biomedical FAIR Data Analysis in the Cloud Using CAVATICA

The historically fragmented biomedical data ecosystem has moved towards harmonization under the findable, accessible, interoperable, and reusable (FAIR) data principles, creating more opportunities for cloud-based research. This shift is especially opportune for scientists across diverse domains interested in implementing creative, nonstandard computational analytic pipelines on large and varied datasets. However, executing custom cloud analyses may present difficulties, particularly for investigators lacking advanced computational expertise. Here, we present an accessible, streamlined approach for the cloud compute platform CAVATICA that offers a solution. We outline how we developed a custom workflow in the cloud, for analyzing whole genome sequences of case-parent trios to detect sex-specific genetic effects on orofacial cleft risk, which required several programming languages and custom software packages. The approach involves just three components: Docker to containerize software environments, tool creation for each analysis step, and a visual workflow editor to weave the tools into a Common Workflow Language (CWL) pipeline. Our approach should be accessible to any investigator with basic computational skills, is readily extended to implement any scalable high-throughput biomedical data analysis in the cloud, and is applicable to other commonly used compute platforms such as BioData Catalyst. We believe our approach empowers versatile data reuse and promotes accelerated biomedical discovery in a time of substantial FAIR data.

Cleft lip Sidedness and the Association with Additional Congenital Malformations

OBJECTIVE

To investigate the association between the sidedness of orofacial clefts and additional congenital malformations.

DESIGN

Linkage of a national registry of cleft births to national administrative data of hospital admissions.

SETTING

National Health Service, England.

PARTICIPANTS

2007 children born with cleft lip ± alveolus (CL ± A) and 2724 with cleft lip and palate (CLP) born between 2000 and 2012.

MAIN OUTCOME MEASURE

The proportion of children with ICD-10 codes for additional congenital malformations by the sidedness (left, right or bilateral) of orofacial clefts.

RESULTS

For CL ± A phenotypes, there was no evidence for a difference in the prevalence of additional anomalies between left (22%, reference), right (22%, aOR 1.02, 95% CI 0.80 to 1.28; P = .90) and bilateral clefts (23%, aOR 1.09, 95% CI 0.75 to 1.57; P = .66). For CLP phenotypes, there was evidence of a lower prevalence of additional malformations in left (23%, reference) compared to right (32%, aOR 1.54, 95% CI 1.25 to 1.91; P < .001) and bilateral clefts (33%, aOR 1.64, 95% CI 1.35 to 1.99; P < .001).

CONCLUSIONS

The prevalence of additional congenital malformations was similar across sidedness subtypes with CL ± A phenotypes but was different for sidedness subtypes within CLP cases. These data support the hypothesis that CL ± A has a different underlying aetiology from CLP and that within the CLP phenotype, right sided CLP may lie closer in aetiology to bilateral CLP than it does to left sided CLP.

The heterogeneous genetic architectures of orofacial clefts

Orofacial clefts (OFCs) are common, affecting 1:1000 live births. OFCs occur across a phenotypic spectrum - including cleft lip (CL), cleft lip and palate (CLP), or cleft palate (CP) - and can be further subdivided based on laterality, severity, or specific structures affected. Herein we review what is known about the genetic architecture underlying each of these subtypes, considering both shared and subtype-specific risks. While there are more known genetic similarities between CL and CLP than CP, recent research supports both shared and subtype-specific genetic risk factors within and between phenotypic classifications of OFCs. Larger sample sizes and deeper phenotyping data will be of increasing importance for the discovery of novel genetic risk factors for OFCs and various subtypes going forward.

Genetic association and functional validation of ZFP36L2 in non-syndromic orofacial cleft subtypes

BACKGROUND

Non-syndromic orofacial cleft (NSOC) is one of the most common craniofacial malformations with complex etiology. This study aimed to explore the role of specific SNPs in ZFP36L2 and its functional relevance in zebrafish models.

METHODS

We analyzed genetic data of the Chinese Han population from two previous GWAS, comprising of 2512 cases and 2255 controls. Based on the Hardy-Weinberg Equilibrium (HWE) and minor allele frequency (MAF), SNPs in the ZFP36L2 were selected for association analysis. In addition, zebrafish models were used to clarify the in-situ expression pattern of zfp36l2 and the impact of its Morpholino-induced knockdown.

RESULTS

Via association analysis, rs7933 in ZFP36L2 was significantly associated with various non-syndromic cleft lip-only subtypes, potentially conferring a protective effect. Zebrafish embryos showed elevated expression of zfp36l2 in the craniofacial region during critical stages of oral cavity formation. Furthermore, Morpholino-induced knockdown of zfp36l2 led to craniofacial abnormalities, including cleft lip, which was partially rescued by the addition of zfp36l2 mRNA.

CONCLUSION

Our findings highlight the significance of ZFP36L2 in the etiology of NSOC, supported by both human genetic association data and functional studies in zebrafish. These results pave the way for further exploration of targeted interventions for craniofacial malformations.

Genetic variants in BCL-2 family genes influence the risk of non-syndromic cleft lip with or without cleft palate

BACKGROUND

The BCL-2 family is crucial for cell death regulation and is involved in development, tissue homeostasis, and immunity. This study aimed to investigate the association between genetic variants in BCL-2 family genes and non-syndromic cleft lip with or without cleft palate (NSCL/P) risk.

METHODS

A two-stage case-control study was conducted in this association study. Gene-based analysis using Multi-marker Analysis of GenoMic Annotation was performed in the first stage cohort, which included 565 cases and 1269 controls. A logistic regression model was employed to assess the effect of single nucleotide polymorphisms (SNPs) on susceptibility to NSCL/P. Candidate SNPs were replicated by extra dbGaP case-parent trios. Haploreg, RegulomeDB, and UCSC Genome Browser were used to identify enhancer effects of promising SNPs. Bulk RNA sequencing data obtained from the Gene Expression Omnibus was used to identify co-expressed genes. Single-cell RNA sequencing dataset was used to infer the cell population of the candidate gene. The "Monocle" package was used to analyze the pseudotime cell trajectories.

RESULTS

Rs3943258 located in the enhancer region was associated with the risk of NSCL/P (Pmeta  = 5.66 × 10-04 ) and exhibited an eQTL effect for BCL2 (P = 3.96 × 10-02 ). Co-expression and pathway enrichment analysis revealed that genes related to Bcl2 were significantly enriched in the PI3K-Akt signaling pathway, MAPK signaling pathway, and Wnt signaling pathway. Five cell clusters were identified in single-cell RNA sequencing, and Bcl2 was mainly located in the mesenchyme.

CONCLUSION

The rs3943258 located within BCL2 was probably related to NSCL/P susceptibility.

Sidedness in Unilateral Orofacial Clefts: A Systematic Scoping Review

OBJECTIVE

An overview of the literature relating to the sidedness of unilateral cleft lip with or without cleft palate to map current knowledge on the cause and impact of directional asymmetry.

DESIGN

Scoping review with a systematic search of Medline and Embase from inception to May 2023.

PATIENTS, PARTICIPANTS

Humans born with a left or right unilateral cleft lip with or without a cleft palate.

MAIN OUTCOME MEASURES

Cleft sidedness as a co-occurrence, an outcome or an exposure.

RESULTS

Forty studies were eligible for inclusion and confirmed the predilection for the occurrence of left sided cleft lips; 12 studies reported cleft sidedness co-occurring with another phenotype, 11 studies report sidedness as an outcome and 17 studies as an exposure. Phenotypes which were reported to co-occur with either left or right sided clefts included congenital dental anomalies, handedness and additional congenital anomalies. Variables investigated as a potential cause of left or right sided clefts as an outcome included chromosomal anomalies, genetic variants and environmental factors. Outcomes investigated in relation to cleft sidedness as an exposure included facial anatomical features, facial growth, educational attainment, functional and psychological characteristics. More studies showed worse outcomes in right sided clefts versus left sided clefts than vice versa, although studies were inconsistent, and a quality assessment was not performed.

CONCLUSIONS

The field of cleft sidedness research is expanding and there are promising early findings to differentiate cause and outcome by sidedness of the cleft.

MMP16 as NSCL ± P Susceptible Gene in Western Han Chinese

OBJECTIVE

The role of MMP16 in lip development is unclear. This study aimed to identify nonsyndromic cleft lip with or without palate (NSCL ± P) susceptible loci of MMP16 in western Han Chinese.

DESIGN

We performed targeted sequencing around MMP16 combined with a 2-phase association analysis on common variants. Phase 2 association analysis was performed with NSCL ± P specific subphenotypes (NSCL and NSCLP). Then we used rare variants burden analysis and genotyping, accompanied by motif analysis.

SETTING

This study was completed in a tertiary medical center.

PATIENTS, PARTICIPANTS

Phase 1 targeted sequencing included 159 patients with NSCL ± P and 542 normal controls; phase 2 included 1626 patients with NSCL ± P (1047 NSCL and 579 NSCLP) and 2255 normal controls.

INTERVENTIONS

Venous blood samples were collected from patients and used to extract DNA.

MAIN OUTCOME MEASURES

After Bonferroni correction, phase 1 significant threshold of p-value was 4.28 × 10-5 (0.05/1167 single nucleotide polymorphisms [SNPs]), and phase 2 was .00025 (0.05/200 SNPs). Burden analysis significant threshold p-value was .05.

RESULTS

Common variants phase 1 association analysis identified 11 statistically significant SNPs (lowest p = 1.90 × 10-9, odds ratio (OR) = 0.27, 95% CI: 0.17-0.44), phase 2 replication identified 16 SNPs in NSCL ± P (lowest p = 6.26 × 10-6, OR = 0.77, 95% CI: 0.69-0.86) and 9 in NSCL (lowest p = 8.44 × 10-5, OR = 0.76, 95% CI: 0.66-0.87). Rare variants burden analysis showed no significant results, genotyping results showed they were maternally inherited.

CONCLUSIONS

Our study identified MMP16 susceptible SNPs in NSCL ± P and NSCL, emphasizing its potential role in lip development. Our study also highlighted the importance to perform association analysis with subphenotypes divided.

Ezh2-dependent methylation in oral epithelia promotes secondary palatogenesis

BACKGROUND

In addition to genomic risk variants and environmental influences, increasing evidence suggests epigenetic modifications are important for orofacial development and their alterations can contribute to orofacial clefts. Ezh2 encodes a core catalytic component of the Polycomb repressive complex responsible for addition of methyl marks to Histone H3 as a mechanism of repressing target genes. The role of Ezh2 in orofacial clefts remains unknown.

AIMS

To investigate the epithelial role of Ezh2-dependent methylation in secondary palatogenesis.

METHODS

We used conditional gene-targeting methods to ablate Ezh2 in the surface ectoderm-derived oral epithelium of mouse embryos. We then performed single-cell RNA sequencing combined with immunofluorescence and RT-qPCR to investigate gene expression in conditional mutant palate. We also employed double knockout analyses of Ezh1 and Ezh2 to address if they have synergistic roles in palatogenesis.

RESULTS

We found that conditional inactivation of Ezh2 in oral epithelia results in partially penetrant cleft palate. Double knockout analyses revealed that another family member Ezh1 is dispensable in orofacial development, and it does not have synergistic roles with Ezh2 in palatogenesis. Histochemistry and single-cell RNA-seq analyses revealed dysregulation of cell cycle regulators in the palatal epithelia of Ezh2 mutant mouse embryos disrupts palatogenesis.

CONCLUSION

Ezh2-dependent histone H3K27 methylation represses expression of cell cycle regulator Cdkn1a and promotes proliferation in the epithelium of the developing palatal shelves. Loss of this regulation may perturb movement of the palatal shelves, causing a delay in palate elevation which may result in failure of the secondary palate to close altogether.

Association between IRF6, TP63, GREM1 Gene Polymorphisms and Non-Syndromic Orofacial Cleft Phenotypes in Vietnamese Population: A Case-Control and Family-Based Study

This study aims to identify potential variants in the TP63-IRF6 pathway and GREM1 for the etiology of non-syndromic orofacial cleft (NSOFC) among the Vietnamese population. By collecting 527 case-parent trios and 527 control samples, we conducted a stratified analysis based on different NSOFC phenotypes, using allelic, dominant, recessive and over-dominant models for case-control analyses, and family-based association tests for case-parent trios. Haplotype and linkage disequilibrium analyses were also conducted. IRF6 rs2235375 showed a significant association with an increased risk for non-syndromic cleft lip and palate (NSCLP) and cleft lip with or without cleft palate (NSCL/P) in the G allele, with pallele values of 0.0018 and 0.0003, respectively. Due to the recessive model (p = 0.0011) for the NSCL/P group, the reduced frequency of the GG genotype of rs2235375 was associated with a protective effect against NSCL/P. Additionally, offspring who inherited the G allele at rs2235375 had a 1.34-fold increased risk of NSCL/P compared to the C allele holders. IRF6 rs846810 and a G-G haplotype at rs2235375-rs846810 of IRF6 impacted NSCL/P, with p-values of 0.0015 and 0.0003, respectively. In conclusion, our study provided additional evidence for the association of IRF6 rs2235375 with NSCLP and NSCL/P. We also identified IRF6 rs846810 as a novel marker associated with NSCL/P, and haplotypes G-G and C-A at rs2235375-rs846810 of IRF6 associated with NSOFC.

Genome-wide meta-analyses identify five new risk loci for nonsyndromic orofacial clefts in the Chinese Han population

BACKGROUND

Nonsyndromic orofacial clefts (NSOFCs) are the most common craniofacial birth malformations in humans and are generally classified as nonsyndromic cleft lip with or without cleft palate (NSCL/P) and nonsyndromic cleft palate only (NSCPO). Genome-wide association studies (GWASs) of NSOFCs have demonstrated multiple risk loci and candidate genes; however, published risk factors are able to explain only a small fraction of the observed NSOFCs heritability.

METHODS

Here, we performed GWASs of 1615 NSCPO cases and 2340 controls, and then conducted genome-wide meta-analyses of NSOFCs, totaling 6812 NSCL/P cases, 2614 NSCPO cases, and 19,165 controls from the Chinese Han population.

RESULTS

We identify 47 risk loci with genome-wide pmeta -value <5.0 × 10-8 , 5 risk loci (1p32.1, 3p14.1, 3p14.3, 3p21.31, and 13q22.1) of which are new. All of the 47 susceptibility loci conjointly account for 44.12% of the NSOFCs' heritability in the Chinese Han population.

CONCLUSION

Our results improve the comprehending of genetic susceptibility to NSOFCs and provide new views into the genetic etiology of craniofacial anomalies.

Translational Research Techniques for the Facial Plastic Surgeon: An Overview

The field of facial plastic and reconstructive surgery (FPRS) is an incredibly diverse, multispecialty field that seeks innovative and novel solutions for the management of physical defects on the head and neck. To aid in the advancement of medical and surgical treatments for these defects, there has been a recent emphasis on the importance of translational research. With recent technological advancements, there are now a myriad of research techniques that are widely accessible for physician and scientist use in translational research. Such techniques include integrated multiomics, advanced cell culture and microfluidic tissue models, established animal models, and emerging computer models generated using bioinformatics. This study discusses these various research techniques and how they have and can be used for research in the context of various important diseases within the field of FPRS.

Genetic Inheritance Models of Non-Syndromic Cleft Lip with or without Palate: From Monogenic to Polygenic

Non-syndromic cleft lip with or without palate (NSCL/P) is a prevalent birth defect that affects 1/500-1/1400 live births globally. The genetic basis of NSCL/P is intricate and involves both genetic and environmental factors. In the past few years, various genetic inheritance models have been proposed to elucidate the underlying mechanisms of NSCL/P. These models range from simple monogenic inheritance to more complex polygenic inheritance. Here, we present a comprehensive overview of the genetic inheritance model of NSCL/P exemplified by representative genes and regions from both monogenic and polygenic perspectives. We also summarize existing association studies and corresponding loci of NSCL/P within the Chinese population and highlight the potential of utilizing polygenic risk scores for risk stratification of NSCL/P. The potential application of polygenic models offers promising avenues for improved risk assessment and personalized approaches in the prevention and management of NSCL/P individuals.

Global perspectives in orofacial cleft management and research

Orofacial clefts (OFCs) refer to clefts of the lip and palate, a heterogeneous group of relatively common congenital conditions that can cause mortality and significant disability if untreated, and residual morbidity even when treated with multidisciplinary care. Contemporary challenges in the field include: lack of awareness of OFCs in remote, rural and impoverished populations; uncertainties due to lack of surveillance and data gathering infrastructure; inequitable access to care in some parts of the world; and lack of political will combined with lack of capacity to prioritise research.OFCs present clinically as either syndromic or non-syndromic, with the latter either being isolated or in conjunction with other malformations; however, many registries still do not differentiate between these fundamentally different entities and lump a spectrum of cleft types and sub-phenotypes together. This has implications for treatment, research and ultimately, quality improvement.This paper deals with the challenges in contemporary management in terms of care and the prospects and possibilities for primary prevention of non-syndromic clefts. In terms of management and optimal care, there are also challenges in the provision of multi-disciplinary treatment and management of the consequences of being born with OFCs, such as dental caries, malocclusion and psychosocial adjustment.

Genome Analysis Using Whole-Exome Sequencing of Non-Syndromic Cleft Lip and/or Palate from Malagasy Trios Identifies Variants Associated with Cilium-Related Pathways and Asian Genetic Ancestry

Background: Orofacial clefts (OFCs) are common congenital disabilities that can occur as isolated non-syndromic events or as part of Mendelian syndromes. OFC risk factors vary due to differences in regional environmental exposures, genetic variants, and ethnicities. In recent years, significant progress has been made in understanding OFCs, due to advances in sequencing and genotyping technologies. Despite these advances, very little is known about the genetic interplay in the Malagasy population. Methods: Here, we performed high-resolution whole-exome sequencing (WES) on non-syndromic cleft lip with or without palate (nCL/P) trios in the Malagasy population (78 individuals from 26 families (trios)). To integrate the impact of genetic ancestry admixture, we computed both global and local ancestries. Results: Participants demonstrated a high percentage of both African and Asian admixture. We identified damaging variants in primary cilium-mediated pathway genes WNT5B (one family), GPC4 (one family), co-occurrence in MSX1 (five families), WDR11 (one family), and tubulin stabilizer SEPTIN9 (one family). Furthermore, we identified an autosomal homozygous damaging variant in PHGDH (one family) gene that may impact metabiotic activity. Lastly, all variants were predicted to reside on local Asian genetic ancestry admixed alleles. Conclusion: Our results from examining the Malagasy genome provide limited support for the hypothesis that germline variants in primary cilia may be risk factors for nCL/P, and outline the importance of integrating local ancestry components better to understand the multi-ethnic impact on nCL/P.

Identification of putative regulatory single-nucleotide variants in NTN1 gene associated with NSCL/P

Non-syndromic cleft lip with or without cleft palate (NSCL/P) is a common polygenetic disease. Although genome-wide association studies (GWAS) identified NTN1 gene as a high-priority candidate of NSCL/P, the comprehensive genetic architecture of NTN1 weren't yet known. Thus, this study aimed to determine full-scale genetic variants of NTN1 for NSCL/P in Chinese Han people. Initially, targeted sequencing of NTN1 gene was performed on 159 NSCL/P patients to identify susceptible single nucleotide polymorphisms (SNPs) associated with NSCL/P. Then, association analysis and burden analysis were separately used to validate the common variants and rare variants identified among large size of samples (1608 NSCL/P cases and 2255 controls). Additionally, NSCL/P subtype association analysis was applied to elucidate the etiology discrepancy of non-syndromic cleft lip with palate (NSCLP) and non-syndromic cleft lip only (NSCLO). Lastly, bioinformatics analysis was performed to annotate and prioritize candidate variants. We found 15 NSCL/P-associated SNPs including rs4791774 (P = 1.10E-08, OR = 1.467, 95% CI: 1.286~1.673) and rs9788972 (P = 1.28E-07, OR = 1.398, 95% CI : 1.235~1.584) originally detected by previous GWASs in Chinese Han ancestry. Four NSCLO risk-associated SNPs and eight specific NSCLP associated SNPs were found. Three SNPs (rs4791331, rs4791774 and rs9900753) were predicted to locate at regulatory region of NTN1. Our study validated the association between NTN1 gene and pathogenesis of NSCL/P and reinforced the hypothesis that NSCLP have a different etiology from NSCLO. We also identified three putative regulatory SNPs in NTN1 gene.

Maternal Transmission of the PAX7 Single Nucleotide Polymorphisms among Indian Cleft Trios

Cleft lip and/or cleft palate (CL/P) is one of the most common congenital anomalies of the human face with a complex etiology involving multiple genetic and environmental factors. Several studies have shown the association of the paired box 7 ( PAX7 ) gene with CL/P in different populations worldwide. However, the current literature reveals no reported case-parent trio studies to evaluate the association between the PAX7 gene and the risk of nonsyndromic cleft lip and/or palate (NSCL/P) in the Indian population. Hence, the purpose of this study was to assess the PAX7 gene single nucleotide polymorphisms (SNPs) in the etiology of NSCL/P among the Indian cleft trios. Forty Indian case-parent trios of NSCL/P were included. The cases and their parents' genomic DNA were extracted. The SNPs rs9439714, rs1339062, rs6695765, rs742071, and rs618941of the PAX7 gene were genotyped using the Agena Bio MassARRAY analysis. The allelic transmission disequilibrium test was performed using PLINK software while pair-wise linkage disequilibrium by the Haploview program. The SNP rs9439714 showed evidence of association ( p -value = 0.02, odds ratio = 3) with NSCL/P. Considering the parent-of-origin effects, the SNPs rs9439714 and rs618941 showed an excess maternal transmission of allele C at rs9439714 ( p -value = 0.05) and G allele at rs618941 ( p -value = 0.04). The results of the present study suggested that the SNPs rs9439714 and rs618941 showed an excess maternal transmission of alleles suggestive of the possible role of the PAX7 gene involvement in the etiology of NSCL/P in the Indian population.

Prioritization of non-coding elements involved in non-syndromic cleft lip with/without cleft palate through genome-wide analysis of de novo mutations

Non-syndromic cleft lip with/without cleft palate (nsCL/P) is a highly heritable facial disorder. To date, systematic investigations of the contribution of rare variants in non-coding regions to nsCL/P etiology are sparse. Here, we re-analyzed available whole-genome sequence (WGS) data from 211 European case-parent trios with nsCL/P and identified 13,522 de novo mutations (DNMs) in nsCL/P cases, 13,055 of which mapped to non-coding regions. We integrated these data with DNMs from a reference cohort, with results of previous genome-wide association studies (GWASs), and functional and epigenetic datasets of relevance to embryonic facial development. A significant enrichment of nsCL/P DNMs was observed at two GWAS risk loci (4q28.1 (p = 8 × 10-4) and 2p21 (p = 0.02)), suggesting a convergence of both common and rare variants at these loci. We also mapped the DNMs to 810 position weight matrices indicative of transcription factor (TF) binding, and quantified the effect of the allelic changes in silico. This revealed a nominally significant overrepresentation of DNMs (p = 0.037), and a stronger effect on binding strength, for DNMs located in the sequence of the core binding region of the TF Musculin (MSC). Notably, MSC is involved in facial muscle development, together with a set of nsCL/P genes located at GWAS loci. Supported by additional results from single-cell transcriptomic data and molecular binding assays, this suggests that variation in MSC binding sites contributes to nsCL/P etiology. Our study describes a set of approaches that can be applied to increase the added value of WGS data.

Analysis of candidate genes for cleft lip ± cleft palate using murine single-cell expression data

Introduction: Cleft lip ± cleft palate (CL/P) is one of the most common birth defects. Although research has identified multiple genetic risk loci for different types of CL/P (i.e., syndromic or non-syndromic forms), determining the respective causal genes and understanding the relevant functional networks remain challenging. The recent introduction of single-cell RNA sequencing (scRNA-seq) has provided novel opportunities to study gene expression patterns at cellular resolution. The aims of our study were to: (i) aggregate available scRNA-seq data from embryonic mice and provide this as a resource for the craniofacial community; and (ii) demonstrate the value of these data in terms of the investigation of the gene expression patterns of CL/P candidate genes. Methods and Results: First, two published scRNA-seq data sets from embryonic mice were re-processed, i.e., data representing the murine time period of craniofacial development: (i) facial data from embryonic day (E) E11.5; and (ii) whole embryo data from E9.5-E13.5 from the Mouse Organogenesis Cell Atlas (MOCA). Marker gene expression analyses demonstrated that at E11.5, the facial data were a high-resolution representation of the MOCA data. Using CL/P candidate gene lists, distinct groups of genes with specific expression patterns were identified. Among others we identified that a co-expression network including Irf6, Grhl3 and Tfap2a in the periderm, while it was limited to Irf6 and Tfap2a in palatal epithelia, cells of the ectodermal surface, and basal cells at the fusion zone. The analyses also demonstrated that additional CL/P candidate genes (e.g., Tpm1, Arid3b, Ctnnd1, and Wnt3) were exclusively expressed in Irf6+ facial epithelial cells (i.e., as opposed to Irf6- epithelial cells). The MOCA data set was finally used to investigate differences in expression profiles for candidate genes underlying different types of CL/P. These analyses showed that syndromic CL/P genes (syCL/P) were expressed in significantly more cell types than non-syndromic CL/P candidate genes (nsCL/P). Discussion: The present study illustrates how scRNA-seq data can empower research on craniofacial development and disease.

Gene×environment associations in orofacial clefting

This chapter reviews the evidence of gene×environment interactions (G×E) in the etiology of orofacial cleft birth defects (OFCs), specifically cleft lip (CL), cleft palate (CP), and cleft lip with or without cleft palate (CL/P). We summarize the current state of our understanding of the genetic architecture of nonsyndromic OFCs and the evidence that maternal exposures during pregnancy influence risk of OFCs. Further, we present possible candidate gene pathways for these exposures including metabolism of folates, metabolism of retinoids, retinoic acid receptor signaling, aryl hydrocarbon receptor signaling, glucocorticoid receptor signaling, and biotransformation and transport. We review genes in these pathways with prior evidence of association with OFCs, genes with evidence from prior candidate gene G×E studies, and genes identified from genome-wide searches specifically for identifying G×E. Finally, we suggest future directions for G×E research in OFCs.

Variant analyses of candidate genes in orofacial clefts in multi-ethnic populations

OBJECTIVES

Cleft lip with/without cleft palate and cleft palate only is congenital birth defects where the upper lip and/or palate fail to fuse properly during embryonic facial development. Affecting ~1.2/1000 live births worldwide, these orofacial clefts impose significant social and financial burdens on affected individuals and their families. Orofacial clefts have a complex etiology resulting from genetic variants combined with environmental covariates. Recent genome-wide association studies and whole-exome sequencing for orofacial clefts identified significant genetic associations and variants in several genes. Of these, we investigated the role of common/rare variants in SHH, RORA, MRPL53, ACVR1, and GDF11.

MATERIALS AND METHODS

We sequenced these five genes in 1255 multi-ethnic cleft lip with/without palate and cleft palate only samples in order to find variants that may provide potential explanations for the missing heritability of orofacial clefts. Rare and novel variants were further analyzed using in silico predictive tools.

RESULTS

Ninteen total variants of interest were found, with variant types including stop-gain, missense, synonymous, intronic, and splice-site variants. Of these, 3 novel missense variants were found, one in SHH, one in RORA, and one in GDF11.

CONCLUSION

This study provides evidence that variants in SHH, RORA, MRPL53, ACVR1, and GDF11 may contribute to risk of orofacial clefts in various populations.

Decoding the Human Face: Progress and Challenges in Understanding the Genetics of Craniofacial Morphology

Variations in the form of the human face, which plays a role in our individual identities and societal interactions, have fascinated scientists and artists alike. Here, we review our current understanding of the genetics underlying variation in craniofacial morphology and disease-associated dysmorphology, synthesizing decades of progress on Mendelian syndromes in addition to more recent results from genome-wide association studies of human facial shape and disease risk. We also discuss the various approaches used to phenotype and quantify facial shape, which are of particular importance due to the complex, multipartite nature of the craniofacial form. We close by discussing how experimental studies have contributed and will further contribute to our understanding of human genetic variation and then proposing future directions and applications for the field.

Polygenic risk impacts PDGFRA mutation penetrance in non-syndromic cleft lip and palate

Non-syndromic cleft lip with or without cleft palate (NSCL/P) is a common, severe craniofacial malformation that imposes significant medical, psychosocial and financial burdens. NSCL/P is a multifactorial disorder with genetic and environmental factors playing etiologic roles. Currently, only 25% of the genetic variation underlying NSCL/P has been identified by linkage, candidate gene and genome-wide association studies. In this study, whole-genome sequencing and genome-wide genotyping followed by polygenic risk score (PRS) and linkage analyses were used to identify the genetic etiology of NSCL/P in a large three-generation family. We identified a rare missense variant in PDGFRA (c.C2740T; p.R914W) as potentially etiologic in a gene-based association test using pVAAST (P = 1.78 × 10-4) and showed decreased penetrance. PRS analysis suggested that variant penetrance was likely modified by common NSCL/P risk variants, with lower scores found among unaffected carriers. Linkage analysis provided additional support for PRS-modified penetrance, with a 7.4-fold increase in likelihood after conditioning on PRS. Functional characterization experiments showed that the putatively causal variant was null for signaling activity in vitro; further, perturbation of pdgfra in zebrafish embryos resulted in unilateral orofacial clefting. Our findings show that a rare PDGFRA variant, modified by additional common NSCL/P risk variants, have a profound effect on NSCL/P risk. These data provide compelling evidence for multifactorial inheritance long postulated to underlie NSCL/P and may explain some unusual familial patterns.

Whole-genome sequencing reveals de-novo mutations associated with nonsyndromic cleft lip/palate

The majority (85%) of nonsyndromic cleft lip with or without cleft palate (nsCL/P) cases occur sporadically, suggesting a role for de novo mutations (DNMs) in the etiology of nsCL/P. To identify high impact protein-altering DNMs that contribute to the risk of nsCL/P, we conducted whole-genome sequencing (WGS) analyses in 130 African case-parent trios (affected probands and unaffected parents). We identified 162 high confidence protein-altering DNMs some of which are based on available evidence, contribute to the risk of nsCL/P. These include novel protein-truncating DNMs in the ACTL6A, ARHGAP10, MINK1, TMEM5 and TTN genes; as well as missense variants in ACAN, DHRS3, DLX6, EPHB2, FKBP10, KMT2D, RECQL4, SEMA3C, SEMA4D, SHH, TP63, and TULP4. Many of these protein-altering DNMs were predicted to be pathogenic. Analysis using mouse transcriptomics data showed that some of these genes are expressed during the development of primary and secondary palate. Gene-set enrichment analysis of the protein-altering DNMs identified palatal development and neural crest migration among the few processes that were significantly enriched. These processes are directly involved in the etiopathogenesis of clefting. The analysis of the coding sequence in the WGS data provides more evidence of the opportunity for novel findings in the African genome.

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.

Revisiting the embryogenesis of lip and palate development

Clefts of the lip and palate (CLP), the major causes of congenital facial malformation globally, result from failure of fusion of the facial processes during embryogenesis. With a prevalence of 1 in 500-2500 live births, CLP causes major morbidity throughout life as a result of problems with facial appearance, feeding, speaking, obstructive apnoea, hearing and social adjustment and requires complex, multi-disciplinary care at considerable cost to healthcare systems worldwide. Long-term outcomes for affected individuals include increased mortality compared with their unaffected siblings. The frequent occurrence and major healthcare burden imposed by CLP highlight the importance of dissecting the molecular mechanisms driving facial development. Identification of the genetic mutations underlying syndromic forms of CLP, where CLP occurs in association with non-cleft clinical features, allied to developmental studies using appropriate animal models is central to our understanding of the molecular events underlying development of the lip and palate and, ultimately, how these are disturbed in CLP.

Association of soluble epoxide hydrolase 2 gene with the risk of non-syndromic cleft lip with or without cleft palate in western Han Chinese population

OBJECTIVES

This study aimed to explore the associations between soluble epoxide hydrolase 2 gene (EPHX2) variants and non-syndromic cleft lip with or without cleft palate (NSCL/P) in Chinese Han population.

METHODS

We recruited 159 NSCL/P cases from Chinese Han population and carried out targeted resequencing using the whole genome sequencing data of 542 healthy Chinese individuals from Novegene internal database as controls. We classified EPHX2 variants as common or rare according to their minor allele frequency and performed an association analysis for common variations and a burden analysis for rare variations.

RESULTS

The lowest P-value in NSCL/P was observed at rs57699806 (P=0.000 13, OR=2.849 and 95% CI: 1.691-4.800), followed by rs4732723 (P=0.006 50, OR=0.662 and 95%CI: 0.491-0.892), rs7829267 (P=0.009 20, OR=1.496 and 95%CI: 1.117-2.005), rs721619 (P=0.011 00, OR=1.474 and 95%CI: 1.098-1.980), and rs7816586 (P=0.040 00, OR=1.310 and 95%CI: 1.015-1.691). The odds ratios suggested the C allele at rs4732723 as a protective factor for NSCL/P and the reference alleles at other single nucleotide polymorphisms (SNPs) as the risk factors for NSCL/P. Burden analysis showed no statistical significance (P>0.05).

CONCLUSIONS

Through targeted resequencing, this study identified five SNPs named rs57699806, rs4732723, rs7829267, rs721619, and rs7816586 around the region of EPHX2 gene associated with NSCL/P in Chinese Han population. Four SNPs of rs57699806, rs4732723, rs7829267, and rs7816586 were first identified.

GWAS of thyroid dysgenesis identifies a risk locus at 2q33.3 linked to regulation of Wnt signaling

Congenital hypothyroidism due to thyroid dysgenesis (TD), presented as thyroid aplasia, hypoplasia or ectopia, is one of the most prevalent rare diseases with an isolated organ malformation. The pathogenesis of TD is largely unknown, although a genetic predisposition has been suggested. We performed a genome-wide association study (GWAS) with 142 Japanese TD cases and 8380 controls, and found a significant locus at 2q33.3 (top SNP, rs9789446: P = 4.4 × 10-12), which was replicated in a German patient cohort (P = 0.0056). A subgroup analysis showed that rs9789446 confers a risk for thyroid aplasia (per allele odds ratio = 3.17) and ectopia (3.12) but not for hypoplasia. Comprehensive epigenomic characterization of the 72-kb disease-associated region revealed that it was enriched for active enhancer signatures in human thyroid. Analysis of chromosome conformation capture data showed long-range chromatin interactions of this region with promoters of two genes, FZD5 and CCNYL, mediating Wnt signaling. Moreover, the finding that rs9789446 is a thyroid-specific expression quantitative trait loci, adding further evidence for a cis-regulatory function of this region in thyroid tissue. Specifically, because the risk rs9789446 allele is associated with increased thyroidal expression of FDZ5 and CCNYL1 and given the recent demonstration of perturbed early thyroid development following over-activation of Wnt signaling in zebrafish embryos, an enhanced Wnt signaling in risk allele carriers provide a biologically plausible TD mechanism. In conclusion, our work found the first risk locus for TD, exemplifying that in rare diseases with relatively low biological complexity, GWAS may provide mechanistic insights even with a small sample size.

The genetic factors contributing to the risk of cleft lip-cleft palate and their clinical utility

Cleft lip and cleft palate (CL/P) are among the most common congenital malformations in neonates and have syndromic or nonsyndromic forms. Nonsyndromic forms of malformation are being reported to be associated with chromosomal DNA modification by teratogenic exposure and to complex genetic contributions of multiple genes. Syndromic forms are shown to be related to chromosomal aberrations or monogenic diseases. There is a growing body of data illustrating the association of several genes with risk of developing this malformation, including genetic defects in T-box transcription factor-22 (TBX22), interferon regulatory factor-6 (IRF6), and poliovirus receptor-like-1 (PVRL1), responsible for X-linked cleft palate, cleft lip/palate-ectodermal dysplasia syndrome, and Van der Woude and popliteal pterygium syndromes, respectively. Genetic variants in MTR, PCYT1A, ASS1, SLC 25A13, GSTM1, GSTT1, SUMO1 BHMT1, and BHMT2 are being reported to be linked with CL/P risk. The etiology of nonsyndromic CLP is still remained to be unknown, although mutations in candidate genes have been found. Here, we provide an overview about the potential variants to be associated with CL/P for identification of the relative risk of CLP with respect to the basis of genetic background and environmental factors (e.g., dietary factors, alcohol use).

Target sequencing reveals the association between variants in VAX1 and NSCL/P in Chinese population

OBJECTIVE

A significant genetic association between rs7078160 in VAX1 and NSCL/P has been established through genome-wide association studies (GWAS), and we previously replicated the association in the Chinese population. The critical issue in the post-GWAS era is to identify functional variations that have a real impact on disease in the susceptible regions highlighted by GWAS. This study aimed to elucidate functional variants in VAX1 fully.

MATERIALS AND METHODS

Firstly, target sequencing was performed on 159 NSCL/P patients, followed by association analysis to discover disease-associated single nucleotide polymorphisms (SNPs); we then replicated the findings using a larger sample (1626 cases, 2255 controls) and investigated how candidate SNPs affect disease occurrence using extensive annotation databases. Additionally, we compared the genetic profiles of NSCL/P subtypes.

RESULTS

In this study, 6 SNPs in VAX1 were identified to be associated with NSCL/P in the Western Han Chinese population. Five of them were predicted to influence transcriptional factor biding ability and were expression quantitative trait loci (eQTLs) of nearby genes in multiple tissues.

CONCLUSION

The previously reported association between rs7078160 and NSCL/P was successfully replicated. Moreover, our findings firstly revealed that 5 SNPs in VAX1 are associated with NSCL/P in the Western Han Chinese population.

Monogenic Versus Multifactorial Inheritance in the Development of Isolated Cleft Palate: A Whole Genome Sequencing Study

Craniofacial morphogenesis is highly complex, as is the anatomical region involved. Errors during this process, resulting in orofacial clefts, occur in more than 400 genetic syndromes. Some cases of cleft lip and/or palate (CLP) are caused by mutations in single genes; however, complex interactions between genetic and environmental factors are considered to be responsible for the majority of non-syndromic CLP development. The aim of the current study was to identify genetic risk factors in patients with isolated cleft palate (CP) by whole genome sequencing. Patients with isolated CP (n = 30) recruited from the Riga Cleft Lip and Palate Centre, Institute of Stomatology, Riga, were analyzed by whole genome sequencing. Pathogenic or likely pathogenic variants were discovered in genes associated with CP (TBX22, COL2A1, FBN1, PCGF2, and KMT2D) in five patients; hence, rare disease variants were identified in 17% of patients with non-syndromic isolated CP. Our results were relevant to routine genetic counselling practice and genetic testing recommendations. Based on our data, we propose that all newborns with orofacial clefts should be offered genetic testing, at least for a panel of known CLP genes. Only if the results are negative and there is no suggestive family history or additional clinical symptoms (which would support additional exome or genome-wide investigation), should multifactorial empiric recurrence risk prediction tools be applied for families.

Targeted Re-Sequencing of the 2p21 Locus Identifies Non-Syndromic Cleft Lip Only Novel Susceptibility Gene ZFP36L2

rs7590268 present on the 2p21 locus was identified to be associated with non-syndromic cleft lip with or without cleft palate (NSCL/P) in several populations, including the Chinese Han population, indicating that 2p21 was a susceptibility locus for NSCL/P. However, previous studies have only identified common single-nucleotide polymorphism (SNP) within the THADA gene, neglecting the rare variants and other genes in 2p21; thus, this study was designed to investigate additional variants and novel susceptibility genes in 2p21. A total of 159 NSCL/P patients and 542 controls were recruited in the discovery phase, whereas 1830 NSCL/P patients and 2,436 controls were recruited in the replication phase. After targeted region sequencing, we performed association and burden analyses for the common and rare variants, respectively. Furthermore, RNA-seq, proliferation assay and cell cycle analysis were performed to clarify the possible function of the candidate gene ZFP36L2. Association analysis showed that four SNPs were specifically associated with non-syndromic cleft lip only (NSCLO) and two SNPs were associated with both NSCLO and NSCL/P. Burden analysis indicated that ZFP36L2 was associated with NSCLO (p = .0489, OR = 2.41, 95% CI: 0.98–5.90). Moreover, SNPs in the ZFP36L2 targeted gene JUP were also associated with NSCLO. ZFP36L2 also inhibited cell proliferation and induced G2 phase arrest in the GMSM-K cell line. Therefore, we proposed that ZFP36L2 is a novel susceptibility gene of NSCLO in the 2p21 locus, which could lead to NSCLO by modulating cell proliferation and cycle.

Allele-specific transcription factor binding in a cellular model of orofacial clefting

Non-syndromic cleft lip with/without cleft palate (nsCL/P) is a frequent congenital malformation with multifactorial etiology. While recent genome-wide association studies (GWAS) have identified several nsCL/P risk loci, the functional effects of the associated non-coding variants are largely unknown. Furthermore, additional risk loci remain undetected due to lack of power. As genetic variants might alter binding of transcription factors (TF), we here hypothesized that the integration of data from TF binding sites, expression analyses and nsCL/P GWAS might help to (i) identify functionally relevant variants at GWAS loci, and (ii) highlight novel risk variants that have been previously undetected. Analysing the craniofacial TF TFAP2A in human embryonic palatal mesenchyme (HEPM) cells, we identified 2845 TFAP2A ChIP-seq peaks, several of which were located near nsCL/P candidate genes (e.g. MSX1 and SPRY2). Comparison with independent data suggest that 802 of them might be specific to craniofacial development, and genes near these peaks are enriched in processes relevant to nsCL/P. Integration with nsCL/P GWAS data, however, did not show robust evidence for co-localization of common nsCL/P risk variants with TFAP2A ChIP-seq peaks. This data set represents a new resource for the analyses of craniofacial processes, and similar approaches with additional cell lines and TFs could be applied to generate further insights into nsCL/P etiology.

Genetic markers for non-syndromic orofacial clefts in populations of European ancestry: a meta-analysis

To date, the involvement of various genetic markers in the aetiopathogenesis of non-syndromic orofacial cleft (nsOFC) has been extensively studied. In the present study, we focused on studies performed on populations of European ancestry to systematically review the available literature to define relevant genetic risk factors for nsOFC. Eligible studies were obtained by searching Ovid Medline and Ovid Embase. We gathered the genetic markers from population-based case–control studies on nsOFC, and conducted meta-analysis on the repeatedly reported markers. Whenever possible, we performed stratified analysis based on different nsOFC phenotypes, using allelic, dominant, recessive and overdominant genetic models. Effect sizes were expressed as pooled odds ratios (ORs) with 95% confidence intervals (CIs), and p ≤ 0.05 were considered statistically significant. A total of 84 studies were eligible for this systematic review, with > 700 markers included. Of these, 43 studies were included in the meta-analysis. We analysed 47 genetic variants in 30 genes/loci, which resulted in 226 forest plots. There were statistically significant associations between at least one of the nsOFC phenotypes and 19 genetic variants in 13 genes/loci. These data suggest that IRF6, GRHL3, 8q24, VAX1, TGFA, FOXE1, ABCA4, NOG, GREM1, AXIN2, DVL2, WNT3A and WNT5A have high potential as biomarkers of nsOFC in populations of European descent. Although other meta-analyses that included European samples have been performed on a limited number of genetic variants, this study represents the first meta-analysis of all genetic markers that have been studied in connection with nsOFC in populations of European ancestry.