Genetic Factors in Nonsyndromic Orofacial Clefts

Identification of a novel mutation of Platelet-Derived Growth Factor-C (PDGFC) gene in a girl with Non-Syndromic cleft lip and palate

BACKGROUND

Cleft lip with or without cleft palate (CL/CP) is a prevalent congenital malformation. Approximately 16 candidate loci for CL/CP have been identified in both animal models and humans through association or genetic linkage studies. One of these loci is the platelet-derived growth factor-C (PDGFC) gene. In animal models, a mutation in the PDGFC gene has been shown to lead to CL/CP, with PDGF-C protein serving as a growth factor for mesenchymal cells, playing a crucial role in embryogenesis during the induction of neural crest cells. In this study, we present the identification of a novel frameshift mutation in the PDGFC gene, which we hypothesize to be associated with CL/CP, within a consanguineous Iranian family.

CASE PRESENTATION

The proband was a 3-year-old girl with non-syndromic CL/CP. A history of craniofacial clefts was present in her family. Following genetic counseling, karyotype analysis and whole-exome sequencing (WES) were performed. Cytogenetic analysis revealed normal results, while WES analysis showed that the proband carried a homozygous c.546dupA (p.L183fs) mutation in the PDGFC gene. Sanger sequencing confirmed that her parents were carriers of the mutation.

CONCLUSION

The c.546dupA (p.L183fs) mutation of PDGFC has not been previously reported and was not found in human genome databases. We speculate that the c.546dupA mutation of the PDGFC gene, identified in the Iranian patient, may be responsible for the phenotype of non-syndromic CL/CP (ns-CL/CP). Further studies are warranted to explore the specific pathogenesis of the PDGFC mutation in ns-CL/CP.

Analysis of Consanguinity as Risk Factor of Nonsyndromic Cleft Lips with or without Palate

OBJECTIVES

 The etiologies of nonsyndromic cleft lips with or without palate (NS CL/P) are multifactorial, which include consanguineous marriages. The incidence of NS CL/P is relatively high in Indonesia notably in one of Indonesia's tribes whose members frequently marry close cousins. Thus, the purpose of this study is to analysis consanguinity as risk factor of NS CL/P in Sasak tribe, East Lombok, Indonesia MATERIALS AND METHODS:  An observational analysis was made of a collected database of NS CL/P patients treated in social services in regency hospital of Dr. Soejono Selong, East Lombok, Indonesia. Demographic data such as age, gender, address (urban/rural), parent's education, presence or absence of consanguinity, type of clefts, and a three-generation pedigree were collected by interview and hospital medical record. Before analysis, patient information was anonymized and deidentified. From 2016 to 2018, each of 100 cleft and normal subjects with their Sasak parent were audited. The risk factors were analyzed statistically using odds ratio (OR) and chi-squared test.

RESULTS

 Consanguineous marriages identified 54 cases (54%), and 10 cases (10%) out of a total each 100 NS CL/P and controls, respectively. The majority of consanguinity (53.7%) was discovered in marriages between first cousins. NS CL/P cases were statistically linked (p = 0.00) with consanguineous marriages (OR: 10; 95% confidence interval: 1.6-3.1); in which the most prevalent case is unilateral cleft lips.

CONCLUSION

 Consanguineous marriage increases the risk of NS CL/P in Sasak tribe, East Lombok, Indonesia. The development of strategies to educate communities on the impacts of culture-consanguineous marriage is required. The genetic inheritance from their ancestor may be responsible for the increased incidence of NS CL/P.

US air pollution is associated with increased incidence of non-syndromic cleft lip/palate

Maternal cigarette use is associated with the fetal development of orofacial clefts. Air pollution should be investigated for similar causation. We hypothesize that the incidence of non-syndromic cleft lip with or without palate (NSCLP) and non-syndromic cleft palate (NSCP) would be positively correlated with air pollution concentration.

METHODS

The incidence of NSCLP and NSCP per 1000 live births from 2016 to 2020 was extracted from the Centers for Disease Control and Prevention Vital Statistics Database and merged with national reports on air pollution using the Environmental Protection Agency Air Quality Systems annual data. The most commonly reported pollutants were analyzed including benzene, sulfur dioxide (SO2), particulate matter (PM) 2.5, PM 10, ozone (O3), and carbon monoxide (CO). Multivariable negative binomial and Poisson log-linear regression models evaluated the incidence of NSCLP and NSCP as a function of the pollutants, adjusting for race. All p-values are reported with Bonferroni correction.

RESULTS

The median NSCLP incidence was 0.22/1000 births, and isolated NSCP incidence was 0.18/1000 births. For NSCLP, SO2 had a coefficient estimate (CE) of 0.60 (95% CI [0.23, 0.98], p < 0.007) and PM 2.5 had a CE of 0.20 (95% CI [0.10, 0.31], p < 0.005). Among isolated NSCP, no pollutants were found to be significantly associated.

CONCLUSION

SO2 and PM 2.5 were significantly correlated with increased incidence of NSCLP. The American people and perinatal practitioners should be aware of the connection to allow for risk reduction and in utero screening.

Orofacial Clefts: Genetics of Cleft Lip and Palate

Orofacial clefting is considered one of the commonest birth defects worldwide. It presents as cleft lip only, isolated cleft palate or cleft lip and palate. The condition has a diverse genetic background influenced by gene-gene and gene-environment interaction, resulting in two main types, syndromic and nonsyndromic orofacial clefts. Orofacial clefts lead to significant physiological difficulties that affect feeding, speech and language development and other developmental aspects, which results in an increased social and financial burden on the affected individuals and their families. The management of cleft lip and palate is solely based on following a multidisciplinary team approach. In this narrative review article, we briefly summarize the different genetic causes of orofacial clefts and discuss some of the common syndromes and the approach to the management of orofacial clefts.

Factors Associated With an Increased Risk of Facial Malformations

Background Facial anomalies comprise a significant component of birth defects, with oral clefts being the second most common entity in this group. All organ systems within the body can be affected by congenital anomalies, mostly affecting the musculoskeletal system. Birth defects are among the leading causes of infant mortality and morbidity around the world. Objectives To find the factors associated with an increased risk of facial malformations so that steps for improving preventive measures can be taken. Methodology This was a cross-sectional study in which the data were collected from the files of infants admitted to the pediatric department. Data regarding the type of congenital anomaly, maternal investigations done during pregnancy, maternal history of medication, diabetes, hypertension, radiation exposure, smoking, and alcohol history, and family history of congenital anomalies was collected from the files of neonates and from the pediatrician. In the case of unanswered questions, the parent was contacted after 10 days with their consent. Results Of the sample size of 259 children (males: 132; females: 127), 68 (26%) had a cleft lip, 69 (27%) had a cleft palate, 110 (42%) had both cleft lip and palate, five (2%) had a cleft lip with nasal deformity, five (2%) had a cleft lip and palate with nasal deformity, and two (1%) had hypertelorism. Eight percent of neonates with craniofacial malformations had a family history of congenital malformations; 80.7% of neonates had a history of parental consanguinity; and 19.3% were unrelated. In regard to the mothers, 41.3% of the mothers had diabetes, 4% had hypertension, 4% had both gestational diabetes and hypertension, and 55% had neither of these diseases. Of the 55% of mothers with neither disease, 75% were married to their cousins, while 25% were not married within the family. Practical implications This study, highlighting the major factors contributing to the incidence of congenital facial malformations, will educate the community and establish awareness among the younger generation of the top causes of anomalies, therefore making a huge impact on increasing efforts to reduce the prevalence of congenital anomalies. Conclusion Defects of both the cleft lip and palate had the highest prevalence of facial malformations among study subjects (110 patients (42%)). Parental consanguinity is one of the leading factors associated with an increased risk of facial malformations.

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.

Role of PAX7 Gene rs766325 and rs4920520 Polymorphisms in the Etiology of Non-syndromic Cleft Lip and Palate: A Genetic Study

Non-syndromic cleft lip and palate (NSCLP) is one of the most common birth defects in humans with an overall prevalence of ∼1 in 700 live births around the world. The etiology of NSCLP is complex involving multiple genes, environmental factors, and gene-to-gene interactions. Several genome-wide associations (GWA) studies have shown the association of the paired box 7 ( PAX7 ) gene in the etiology of cleft lip and palate in different populations worldwide. However, there are no reported studies on the association between the rs766325 and rs4920520 polymorphisms and the risk of developing NSCLP in the Indian population. Hence, the present study aimed to test for the probable association between rs766325 and rs4920520 polymorphisms among NSCLP Indian population using a case-parent trio design. Forty case-parent trios were selected from the cleft lip and palate center based on the inclusion and exclusion criteria. Genomic DNA was isolated from the cases and their parents. The rs766325 and rs4920520 polymorphisms of the PAX7 gene were analyzed for their association using the MassARRAY analysis. The statistical analysis was done using the PLINK software. The rs766325 and rs4920520 polymorphisms were tested for the Hardy–Weinberg equilibrium. None of the polymorphisms showed any statistical significance. Hence, the rs766325 and rs4920520 polymorphisms of the PAX7 gene were found to be not associated with NSCLP in the Indian case-parent trios.

Orofacial Cleft and Mandibular Prognathism-Human Genetics and Animal Models

Many complex molecular interactions are involved in the process of craniofacial development. Consequently, the network is sensitive to genetic mutations that may result in congenital malformations of varying severity. The most common birth anomalies within the head and neck are orofacial clefts (OFCs) and prognathism. Orofacial clefts are disorders with a range of phenotypes such as the cleft of the lip with or without cleft palate and isolated form of cleft palate with unilateral and bilateral variations. They may occur as an isolated abnormality (nonsyndromic-NSCLP) or coexist with syndromic disorders. Another cause of malformations, prognathism or skeletal class III malocclusion, is characterized by the disproportionate overgrowth of the mandible with or without the hypoplasia of maxilla. Both syndromes may be caused by the presence of environmental factors, but the majority of them are hereditary. Several mutations are linked to those phenotypes. In this review, we summarize the current knowledge regarding the genetics of those phenotypes and describe genotype-phenotype correlations. We then present the animal models used to study these defects.

PAX7, PAX9 and RYK Expression in Cleft Affected Tissue

Background and Objectives: Cleft lip with or without cleft palate is one of the most common types of congenital malformations. Transcription factors paired box 7 and 9 (PAX7, PAX9) and receptor-like tyrosine kinase (RYK) have been previously associated with the formation of orofacial clefts but their exact possible involvement and interactions in the tissue of specific cleft types remains uncertain. There is a limited number of morphological studies analyzing these specific factors in cleft affected tissue due to ethical aspects and the limited amount of available tissue material. This study analyses the presence of PAX7, PAX9, and RYK immunopositive structures within different cleft affected tissue to assess their possible involvement in cleft morphopathogenesis. Materials and Methods: Cleft affected tissue was collected from non-syndromic orofacial cleft patients during cleft correcting surgery (36 patients with unilateral cleft lip, 13 patients with bilateral cleft lip, 26 patients with isolated cleft palate). Control group oral cavity tissue was obtained from 7 patients without cleft lip and palate. To evaluate the number of immunopositive structures in the cleft affected tissue and the control group, a semiquantitative counting method was used. Non-parametric statistical methods (Kruskal–Wallis H test, Mann–Whitney U test, and Spearman’s rank correlation) were used. Results: Statistically significant differences for the number of PAX7, PAX9, and RYK-positive cells were notified between the controls and the patient groups. Multiple statistically significant correlations between the factors were found in each cleft affected tissue group. Conclusions: PAX7, PAX9, and RYK have a variable involvement and interaction in postnatal morphopathogenesis of orofacial clefts. PAX7 is more associated with the formation of unilateral cleft lip, while PAX9 relates more towards the isolated cleft palate. The stable presence of RYK in all cleft types indicates its possible participation in different facial cleft formations.