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Sorting out all the genes that cause mental retardation is a challenge, particularly when unusual inheritance patterns hinder gene identification. When multiple children are affected by a genetic disorder and parents are normal, autosomal recessive inheritance is usually the suspected cause. In this study, researchers describe a mental retardation syndrome that is maternally transmitted (imprinted with paternal silencing). Birk Barel mental retardation syndrome (BBMRS) is characterized by mental retardation; hypotonia; hyperactivity; dysphagia; facial dysmorphism; and elongated neck, trunk, and feet.
Investigators analyzed the genomes of 11 members of one extended family who had BBMRS and 16 members who were healthy. The KCNK9 gene (potassiu…