Environmental factors related to the occurrence of oral clefts in a Brazilian subpopulation

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.

Environmental Factors at the Periconceptional Period and the Occurrence of Cleft Lip and Palate in a Midwest Brazil Population: A Case-Control Study

OBJECTIVE

To investigate the association between periconceptional environmental exposures and the occurrence of cleft lips and palates.

METHODS

This case-control study analyzed 150 mothers of children with cleft lips and palates living in the same city as 250 mothers whose children did not present with this malformation (controls). Environmental exposure data were gathered through a questionnaire (Latin American Collaborative Study of Congenital Malformations methodology).

RESULTS

Multivariate analysis revealed that monthly income below minimum wage, having another malformed child, other diseases in the first gestational trimester (urinary infection), use of pesticides in home gardens, and pesticide use in farms close to the home were risk factors associated with the malformation, whereas taking vitamins was a protective factor.

CONCLUSION

Maternal and paternal exposure to pesticides is associated with cleft lip and palate in Mato Grosso State, Brazil.

Cleft Lip and/or Palate and Associated Risks in Lower-Middle-Income Countries: A Systematic Review

OBJECTIVE

To identify and review published data on the risks associated with cleft lip and/or palate (CL/P) in lower-middle-income countries (LMICs).

DESIGN

A systematic review of literature was performed on electronic databases using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis Protocols. Literature on risks associated with CL/P in LMICs, from 2010 to 2020, were included.

RESULTS

Seventeen studies met the inclusion criteria. All studies adopted an observational study design. Biological and environmental risks were identified. Maternal and paternal age (n = 7) and low socioeconomic status (n = 5) were the most prominently associated environmental risk factors. A strong association was identified between family history of cleft (n = 7) and CL/P occurrence.

CONCLUSION

Environmental risk factors are now being investigated more than biological risk factors in LMICs, aiding health care workers in the early identification of possible cumulative effects of risks in CL/P. Contextually relevant tools are recommended to promote early identification of at-risk infants.

A Retrospective Cohort Study to Evaluate the Association Between Types of Nonsyndromic Oral Clefts and a Child's Gender and Maternal Age

Aims

To evaluate the association between nonsyndromic cleft lip with or without cleft palate (NSCL±P) anomaly and the affected child's gender and maternal age.

Materials and Methods

Records of 141 newborns received at the orthodontic craniofacial clinic of the Jordanian Royal Rehabilitation Center between 2017 and 2019 were retrospectively analyzed. Two variables were paid attention to: child's gender and maternal age. Five cleft types were considered: unilateral CLP (right; URCLP and left; ULCLP), bilateral CLP (BCLP), isolated cleft palate (CP) and isolated cleft lip (CL). Maternal age was classified into four subgroups: "26-30" years, "31-35" years, "36-40" years, and "above 40" years. Chi-square test and multinomial logistic regression analysis were used to analyze the resultant data.

Results

A significant occurrence of the NSCL±P in females was found compared with males. The different cleft types were found to be significantly associated with the different maternal age groups investigated. The ULCLP was the most prevalent cleft type for affected children among all maternal age groups except the "31-35" group, at which the BCLP exceeded.

Conclusions

The children's gender and the maternal age have a significant impact on defining the developing oral cleft types.

The Prevalence of Nonsyndromic Oral Clefts in Twins Compared to Singletons: The Association With Birth Weight

PURPOSE

To examine the prevalence of nonsyndromic oral clefts in twins compared to singletons in the United States and to evaluate the association between birth weight and nonsyndromic oral clefts.

DESIGN

A large population-based cross-sectional study was performed using the data from the US National Center for Health Statistics database in 2017.

PARTICIPANTS

Our sample consisted of 128 310 twins and 3 723 273 singletons.

METHODS

The variables collected were sociodemographic variables, environmental predictors, and clinical measures. Descriptive analysis, bivariate, and multivariate logistic regression were performed.

MAIN OUTCOME MEASURE

The main outcome variable in our study is nonsyndromic oral clefts.

RESULTS

The prevalence of nonsyndromic oral clefts was 5.22 per 10 000 in twins and 5.12 per 10 000 in singletons. Results show no significant risk of nonsyndromic oral clefts in twins compared to singletons (P = .92). There was a significant relationship between birth weight and infant diagnosed with nonsyndromic oral clefts (P = .01). Unadjusted odds ratio for birth weight was 2.52 (95% CI: 2.25-2.82). Adjusted odds for potential confounders such as mother's age, race, mother's education, gender of the infant, APGAR 5-minute score, gestational age, prenatal smoking, number of prenatal care visits, and mother's body mass index were resulted in similar but with a slightly lower odds of 2.11 (95% CI: 1.78-2.50).

CONCLUSION

Compared to singletons, twins did not have higher risk of nonsyndromic oral clefts. Infants with low birth weight were more prone to have nonsyndromic oral clefts.

Environmental mechanisms of orofacial clefts

Orofacial clefts (OFCs) are among the most common birth defects and impart a significant burden on afflicted individuals and their families. It is increasingly understood that many nonsyndromic OFCs are a consequence of extrinsic factors, genetic susceptibilities, and interactions of the two. Therefore, understanding the environmental mechanisms of OFCs is important in the prevention of future cases. This review examines the molecular mechanisms associated with environmental factors that either protect against or increase the risk of OFCs. We focus on essential metabolic pathways, environmental signaling mechanisms, detoxification pathways, behavioral risk factors, and biological hazards that may disrupt orofacial development.

Associations Between Disinfection By-Product Exposures and Craniofacial Birth Defects

OBJECTIVE

The aim of this study was to examine associations between craniofacial birth defects (CFDs) and disinfection by-product (DBP) exposures, including the sum of four trihalomethanes (THM4) and five haloacetic acids (HAA5) (ie, DBP9).

METHODS

We calculated first trimester adjusted odds ratios (aORs) for different DBPs in a matched case-control study of 366 CFD cases in Massachusetts towns with complete 1999 to 2004 THM and HAA data.

RESULTS

We detected elevated aORs for cleft palate with DBP9 (highest quintile aOR = 3.52; 95% CI: 1.07, 11.60), HAA5, trichloroacetic acid (TCAA), and dichloroacetic acid. We detected elevated aORs for eye defects with TCAA and chloroform.

CONCLUSION

This is the first epidemiological study of DBPs to examine eye and ear defects, as well as HAAs and CFDs. The associations for cleft palate and eye defects highlight the importance of examining specific defects and DBPs beyond THM4.

Risk factors and comorbidities in Brazilian patients with orofacial clefts

Considering that environmental risk factors substantially contribute to the etiology of orofacial clefts and that knowledge about the characteristics and comorbidities associated with oral clefts is fundamental to promoting better quality of life, this study aimed to describe the risk factors, main characteristics, and comorbidities of a group of patients with cleft lip and/or cleft palate (CL/P) from Rio Grande do Norte (RN), Brazil. Data were obtained from 173 patients with CL/P using a form from the Brazilian database on Orofacial Clefts. Most patients were male with cleft lip and palate and had a normal size and weight at birth; presented few neonatal intercurrent events; and had anemia and respiratory and cardiovascular diseases as main associated comorbidities. They also required timely surgical rehabilitation and multidisciplinary care to stimulate their neuropsychomotor development. In addition, a high frequency of familial recurrence and of parental consanguinity was evidenced in the studied population, especially for the cleft lip and cleft palate type. Other relevant findings were the considerable maternal exposure to alcohol, infections, smoking, and hypertension, as well as low supplementation with vitamins and minerals and deliberate consumption of analgesics, antibiotics, and antihypertensives during pregnancy. Characterization of the CL/P patient profile is essential for the planning of health services and integration among the health professionals involved in the diagnosis and treatment of these malformations. Our results reinforce the need for additional research to confirm the association between environmental factors and the development of orofacial clefts.

Paternal Risk Factors for Oral Clefts in Northern Africans, Southeast Asians, and Central Americans

While several studies have investigated maternal exposures as risk factors for oral clefts, few have examined paternal factors. We conducted an international multi-centered case–control study to better understand paternal risk exposures for oral clefts (cases = 392 and controls = 234). Participants were recruited from local hospitals and oral cleft repair surgical missions in Vietnam, the Philippines, Honduras, and Morocco. Questionnaires were administered to fathers and mothers separately to elicit risk factor and family history data. Associations between paternal exposures and risk of clefts were assessed using logistic regression adjusting for potential confounders. A father’s personal/family history of clefts was associated with significantly increased risk (adjusted OR: 4.77; 95% CI: 2.41–9.45). No other significant associations were identified for other suspected risk factors, including education (none/primary school v. university adjusted OR: 1.29; 95% CI: 0.74–2.24), advanced paternal age (5-year adjusted OR: 0.98; 95% CI: 0.84–1.16), or pre-pregnancy tobacco use (adjusted OR: 0.96; 95% CI: 0.67–1.37). Although sample size was limited, significantly decreased risks were observed for fathers with selected occupations. Further research is needed to investigate paternal environmental exposures as cleft risk factors.