RESUMO
Cleft palate most commonly occurs as a sporadic multifactorial disorder with a clear but difficult to define genetic component. As a semi-dominant disorder, X-linked cleft palate (CPX) provides a useful model to investigate a congenital defect that is little influenced by non-genetic factors. By using an Icelandic kindred, CPX has been localised between DXS1196 and DXS1217 and mapped, in a 3-Mb yeast artificial chromosome contig, at Xq21.3. Markers generated from this physical map have now been used to construct a contig of P1 and bacterial artificial chromosome clones for genomic DNA sequencing. Genomic DNA sequence analysis has revealed two novel expressed genes and two pseudogenes in the order Cen-KLHL4-LAMRL5-CAPZA1P-CPXCR1-Tel. KLHL4 and CPXCR1 are widely expressed in fetal tissues, including the tongue, mandible and palate. DNA mutation screening of CPXCR1 has revealed several sequence variants present on all affected CPX chromosomes. However, these variants have also been detected at a lower frequency on unaffected chromosomes, indicating that they are polymorphisms that are unlikely to cause the CPX phenotype.
Assuntos
Fissura Palatina/genética , Língua/anormalidades , Cromossomo X/genética , Sequência de Aminoácidos , Bacteriófago P1 , Sequência de Bases , Cromossomos Artificiais Bacterianos , Cromossomos Artificiais de Levedura , Mapeamento de Sequências Contíguas , DNA/química , DNA/genética , Análise Mutacional de DNA , Feminino , Feto/metabolismo , Regulação da Expressão Gênica no Desenvolvimento , Ligação Genética , Humanos , Masculino , Repetições de Microssatélites , Dados de Sequência Molecular , Mutação , Mapeamento Físico do Cromossomo , Polimorfismo Genético , RNA/genética , RNA/metabolismo , Distribuição Tecidual , Transcrição GênicaRESUMO
X-linked cleft palate (CPX) is a rare nonsyndromic form of orofacial clefting that is, unlike more common forms, inherited as a highly penetrant Mendelian trait. Linkage studies using a large Icelandic kindred localized the gene to Xq21.3, and a physical map defining a 2.0-Mb candidate region was subsequently constructed. Genomic sequence is now available for much of the critical region and has been surveyed for potential transcriptional units. Through this analysis, we have identified a novel human homologue of Kelch, KLHL4. The transcript represents a mRNA of approximately 3.6 kb and encodes a protein of 718 amino acids. Protein domain analysis reveals six tandem repeats (Kelch repeats) at the C-terminus and a POZ/BTB protein-binding domain toward the N-terminus, characteristic of Drosophila Kelch and other family members. KLHL4 consists of 11 exons spanning a genomic interval of approximately 150 kb. From EST sequences and RT-PCR analysis, there is evidence for the use of alternative 3' UTRs. The mRNA is expressed in a range of fetal tissues including tongue, palate, and mandible. Mutational analysis in affected CPX patients revealed one sequence alteration that was most likely to be a silent polymorphism.
