Genetic testing and prenatal diagnosis for a Chinese pedigree affected with Meckel-Gruber syndrome / 中华医学遗传学杂志

OBJECTIVE@#To carry out genetic testing and prenatal diagnosis for a Chinese couple whom had conceived two fetuses featuring multiple malformations including polycystic kidney, polydactyly and encephalocele.@*METHODS@#Following elective abortion, the fetus from the second pregnancy was subjected to whole exome sequencing. Suspected pathogenic variants were verified by Sanger sequencing of the fetus and its parents.@*RESULTS@#The fetus was found to harbor compound heterozygous variants of the CEP290 gene, namely c.2743G>T (p.E915X) and c.2587-2A>T, which were respectively inherited from its father and mother. The same variants were not detected among 100 healthy controls nor reported previously. Bioinformatic analysis suggested both variants to be deleterious. The fetus was diagnosed with Meckel-Gruber syndrome. Prenatal diagnosis for the couple during their next pregnancy suggested that the fetus did not carry the above pathogenic variants.@*CONCLUSION@#The compound heterozygous variants of the CEP290 gene probably underlay the pathogenesis of Meckel-Gruber syndrome in the second fetus. Above finding has provided a basis for genetic counseling and prenatal diagnosis for the couple, and also enriched the mutational spectrum of the CEP290 gene.

Mutations in collagen 18A1 (COL18A1) and their relevance to the human phenotype

Colágeno XVIII, uma proteoglicana, é um componente das membranas basais (MBs). Existem três isoformas distintas que diferem apenas na região N-terminal, mas que apresentam um padrão específico de expressão nos diferentes tecidos e durante o desenvolvimento. A clivagem da região C-terminal produz endostatina, um inibidor de angiogênese. Na sua região N-terminal, há um motivo "frizzled'', o qual parece estar envolvido com a sinalização de Wnt. Mutações no gene COL18A1 causam a síndrome de Knobloch (SK), uma condição de herança autossômica recessiva caracterizada por degeneração vítreo - retiniana, degeneração de mácula e encefalocele occipital. Esta revisão discute o efeito tanto de alelos raros como polimórficos no fenótipo, mostrando que deficiência de uma das isoformas de colágeno XVIII é suficiente para causar SK e que alelos nulos causando deficiência de todas as isoformas de colágeno XVIII estão associadas a alterações oculares mais graves. Esta revisão, além de ilustrar a importância funcional do colágeno XVIII no desenvolvimento do olho e na manutenção de sua estrutura, também mostra que esta proteína tem um papel funcional importante em outros tecidos e órgão, como no sistema nervoso central e rim.

Meckel Gruber syndrome: occurrence in non-consanguineous marriages.

Meckel Gruber syndrome is an uncommon, lethal, autosomal recessive disorder, associated consistently with polycystic kidneys, posterior encephalocoele and polydactly. We report three cases in non-consanguineous marriages, suggesting that the single gene defect occurs more commonly in non-consanguineous marriages than mutant genes associated with other autosomal recessive disorders that are usually related with consanguineous marriages. The usefulness of prenatal diagnosis is discussed.

Meckel-Gruber syndrome: a lethal combination of abnormalities

We herein describe two cases of Meckel-Gruber Syndrome identified in stilborn infants. Both had all three elements of the classical triad, namely, occipital encephalocele, renal cystic dysplasia and post-axial polydactyly. In addition, many of the other well-known accompanying abnormalities were present. Awareness of this entity in this region is important because of its high risk of recurrence in subsequent pregnancies