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Study Description

This study provides an opportunity to investigate the genetics of both dental caries and orofacial clefts (OFCs) in one set of families ascertained in Guatemala. This study is part of the Gene Environment Association Studies initiative (GENEVA, http://www.genevastudy.org), which was developed through the trans-NIH Genes, Environment, and Health Initiative (GEI). Furthermore this study brings together multiple research priorities of the University of Pittsburgh Center for Craniofacial and Dental Genetics (www.ccdg.pitt.edu). A genome-wide panel of 610,000 SNPs was genotyped at the Broad Institute to be comparable to our other pertinent GENEVA studies that are also part of dbGaP (dbGaP accession number phs000095, "Dental Caries: Whole Genome Association and Gene x Environment Studies" and dbGaP accession number phs000094, "International Consortium to Identify Genes and Interactions Controlling Oral Clefts"). The goal of this study is to investigate genetic determinants to dental caries and to OFCs in a novel study population. To date, most genetic studies of dental caries have been conducted in Caucasians, and of OFCs in Caucasians and Asians. The Guatemalan population under study is rural and ethnically mixed with a high proportion of Native-South-Americans.

Thirty-six Guatemalans from this dataset were also part of the recent GWAS studies of cleft lip and cleft palate (Beaty et al., 2010 and 2011, dbGaP Study Accession: phs000094, "International Consortium to Identify Genes and Interactions Controlling Oral Clefts"). In addition to the families ascertained in Guatemala, some subjects were genotyped with this cohort to augment the data in the parent GENEVA study (Dental Caries: Whole Genome Association and Gene x Environment Studies, dbGaP accession number phs000095), in particular individuals from the IOWA and PITT GENEVA study sites. Their data are available with the parent study.

Dental caries (also known as tooth decay) remains the most common chronic disease of childhood, five times more common than asthma and seven times more common than environmental allergies, with more than 40% of children exhibiting caries when they enter kindergarten. In 2005, it was estimated that dental health care costs were approximately $84 billion, of which 60% or about $50 billion were related to treatment of dental caries. The etiology of dental caries has been studied for many years. Multiple factors contribute to a person's risk for caries, including: 1) environmental factors such as diet, oral hygiene, fluoride exposure and the level of colonization of cariogenic bacteria and 2) host factors such as salivary flow, salivary buffering capacity, position of teeth relative to each other, surface characteristics of tooth enamel and depth of occlusal fissures on posterior teeth. In spite of all that is known about this disease, there are still individuals who appear to be more susceptible to caries and those who are extremely resistant, regardless of the environmental risk factors to which they are exposed, implying that genetic factors also play an important role in caries etiology. This conclusion is supported by studies in both humans and animals, with the most compelling evidence coming from studies of twins reared apart in which investigators found significant resemblance within monozygotic (MZ) but not dizygotic (DZ) twin pairs for percentage of teeth and surfaces restored or carious and estimated the genetic contribution to caries as 40%. Other recent studies of twins reared together estimated the heritability for caries, adjusted for age and gender, as ranging from 45-64%. In our study populations of families, we also estimated caries heritability as approximately 54%-70% of variation in primary dentition caries scores and 35%-55% in the permanent dentition (Wang et al., 2010).

Orofacial clefts (OFCs), particularly cleft lip with or without cleft palate (CL/P) and isolated cleft palate (CP) are a major public health problem, affecting one in every 500-1000 births worldwide thus representing the most common facial birth defect and one of the most common of all congenital anomalies. CL/P is a major structural birth defect that is notable for significant lifelong morbidity and complex etiology. The extensive psychological, surgical, speech and dental involvement emphasize the importance of understanding the underlying causes of CL/P. Therefore, many research groups have attempted to elucidate the etiology of CL/P, with some recent success by our research group and others (see Beaty et al., 2010, 2011; Dixon et al., 2011). It is clear that CL/P can occur as part of Mendelian syndromes, that certain chromosomal abnormalities include CL/P in the phenotype, and that certain teratogens can increase the risk of having an offspring with CL/P. However, phenotypes of known etiology comprise only a small portion of all individuals with a CL/P or CP, and the major focus of research into OFCs is to develop an understanding of the etiology of nonsyndromic (NS) forms of clefting. A major focus of the University of Pittsburgh CCDG has been to study additional phenotypes within nonsyndromic OFC families in order to identify sub-clinical expressions of OFC risk genes or risk variants, e.g. SNPs (see Weinberg et al., 2006). A detailed oral exam is conducted as part of these extended phenotypic studies, including a dental caries exam.

Note that although there are some reports in the literature of higher caries experience in individuals with clefts, the most recent meta-analysis of those literature reports concluded that individuals born with these defects do not have a higher frequency of caries (Hasslöf and Twetman, 2007). Notably, we investigated the association of CL/P and caries in three of our study populations (including part of the Guatemalan population in this GWAS study) and also found no increase in caries rates of CL/P cases versus controls (Jindal et al., 2011).

This study is part of the Gene Environment Association Studies initiative (GENEVA, http://www.genevastudy.org), which was developed through the trans-NIH Genes, Environment, and Health Initiative (GEI). The overarching goal is to identify novel genetic factors that contribute to dental caries and oral clefts through large-scale genome-wide association studies of well-characterized Guatemalan families and individuals. Genotyping was performed at the Broad Institute of MIT and Harvard. The study was supported by the National Institute of Dental and Craniofacial Research (NIDCR, U01-DE018903). Data cleaning and harmonization were done at the GEI-funded GENEVA Coordinating Center at the University of Washington.

  • Study Type: Nuclear Families
  • Number of study subjects that have individual level data available through Authorized Access: 1304

Authorized Access
Publicly Available Data (Public ftp)

Connect to the public download site. The site contains release notes and manifests. If available, the site also contains data dictionaries, variable summaries, documents, and truncated analyses.

In the course of routine data cleaning and data analyses, investigators may incidentally identify genetic abnormalities that might influence the clinical care of an individual. These statements and recommendations have been developed to help investigators when they are informed of any such incidental findings.

  1. GENEVA Statement on Incidental Findings
  2. GENEVA Aneuploidy Reference Table
  3. GENEVA Pharmacogenetic Variants Reference Table

Study Inclusion/Exclusion Criteria

Families for this study were ascertained in Guatemala. Families were selected based on orofacial cleft status: (1) Case families: one or more family member(s) with cleft lip, cleft palate or both; (2) Control families: families with no known family history of cleft lip or cleft palate.

Families were not ascertained on dental caries, i.e., families were included regardless of their dental caries status.

Molecular Data
TypeSourcePlatformNumber of Oligos/SNPsSNP Batch IdComment
Whole Genome Genotyping Illumina Human610_Quadv1_B 601273 1048904
Study History

The Guatemalan population under study here is part of a large international study conducted by the University of Pittsburgh Center for Craniofacial and Dental Genetics (CCDG, www.ccdg.pitt.edu). This study is known as the Pittsburgh Orofacial Cleft Study (POFC), which began in 2002 and which has data collection sites in several countries (Guatemala, Hungary, Brazil, Argentina, China, the Philippines) the U.S.A. (Pittsburgh, Texas, Iowa). The goal of POFC is to investigate etiologic factors in Orofacial Clefts (OFCs), particularly nonsyndromic cleft lip and cleft palate (CL/P). The major focus of the study is to understand genetic components contributing to risk of CL/P and to understand the underlying heterogeneity in this group of disorders. As a tool for better understanding CL/P, POFC is conducting extensive phenotyping within families with one or more individuals affected with CL/P, and in control families with no known family history of CL/P. The phenotypes under investigation include a variety of sub-clinical phenotypes that are seen in the general population (and in our study control families) but are seen at an increased frequency in relatives of individuals with CL/P compared to controls (Weinberg et al., 2006; Marazita, 2007). Among these sub-clinical phenotypes are several oral measurements, including assessment of dental caries status. Thus, this GWAS allows studies of CL/P and dental caries in the same study population.

The POFC Guatemala site was started as a partnership with a medical service organization, Children of the Americas (www.childrenoftheamericas.org), and their associated Guatemalan hospitals. The Guatemalan families under study have been investigated for some candidate genes for dental caries (Deeley et al., 2007) and for several candidate genes for CL/P (e.g. Neiswanger et al., 2006) as well as being part of the recent GWAS studies of cleft lip and cleft palate (Beaty et al., 2010 and 2011). Note that we investigated the association of CL/P and caries in three of the study populations (including part of the Guatemalan population in this GWAS study) and found no increase in caries rates in CL/P cases versus controls (Jindal et al., 2011).

Selected publications
Diseases/Traits Related to Study (MESH terms)
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