A new study has identified more common genetic variants associated with increased risk for cleft lip and palate. Combined with two previous studies (more here and here), there are now four variations that have been associated with this birth defect that affects about one out of every 700 children born.
Clefting results from improper fusing during fetal development of the different elements that will make up the lower part of the face. For some children only the lip is affected, while others have clefting of both the lip and palate. Cleft palate alone is much more rare.
An international team led by German researchers analyzed the DNA of 399 people born with cleft lip with or without cleft palate and 1,318 controls. Many of these people had been included in one of the previous studies that found a genetic association with clefting. The researchers then examined the most promising variants in 665 families with an affected child. All of the study subjects had European ancestry.
Two SNPs with significant associations were identified. The relative risk of cleft lip with or without cleft palate was 1.36 for one copy of the A version of rs7078160, and 2.50 for two copies. The relative risk was 1.38 for one copy of the G version of rs227731, and 1.91 for two copies. The results were published online yesterday in the journal Nature Genetics.
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Both rs227731 and rs7078160 are located in regions of the genome previously associated with cleft lip and/or palate in animal models and in humans.
There is some evidence that cleft lip with and without cleft palate are two separate conditions, possibly with different genetic risk factors. The authors of the current report did not find any difference between the effects of their most significant genetic associations, including rs227731 and rs7078160. No association of these SNPs was found with cleft palate alone.
The researchers believe that together the previously described variants and these two newly identified SNPs account for a substantial proportion of the risk for sporadic cleft lip with or without cleft palate. However, they think there are probably still additional genetic variants associated with this condition left to be found.
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