الملخص
【Objective】 To analyze the genetic variation characteristics and clinical phenotypes of a family with primary microcephaly (MCPH) caused by RTTN gene variation, and to provide reference for genetic counseling and prenatal diagnosis. 【Methods】 Clinical data of the three patients (including 2 fetuses and 2-year-old proband,and one fetus with clinical diagnosis) and their parents were collected and analyzed. Two of the children and their parents were tested by trio whole exome sequencing (trio-WES), sanger sequencing validation sites, and the hazard of their compound heterozygous variants was predicted. Literature review was conducted through domestic and international databases to collect reported RTTN gene mutation cases. 【Results】 Three patients in this family had anomalies of the septum pellucidum, hypoplasia of the corpus callosum and other brain malformations during fetal period. The proband (G2) and fetus (G3) showed intrauterine growth retardation and MCPH in late pregnancy; besides, G2 was born with global developmental delay. Trio-WES detected a c.2101(exon16)C>T(p.Arg701Ter,1526) nonsense and a c.2863(exon22)G>A(p.Glu955Lys)missense in the RTTN gene of G2 and G3, which were inherited from their father and mother, forming a compound heterozygous variant. According to the American College of Medical Genetics and Genomics (ACMG) variant classification guidelines, two variants were likely to be pathogenic (LP) and uncertain significance (VUS). Among them, c.2863(exon22)G>A was a newly discovered missense, which was predicted by the software to be harmful to the gene product. 【Conclusions】 Complex heterozygous variations of RTTN gene (c.2101C>T and c.2863G>A) are the genetic cause of MCPH in this family. This report has enriched the variation spectrum of RTTN gene, provided guidance for prenatal diagnosis and reproduction of this family, as well as material and reference for further understanding of the diseases caused by this gene mutation.
الملخص
OBJECTIVE@#To explore the genetic basis for a child with multiple malformations.@*METHODS@#A child who had presented at Shanxi Provincial Children's Hospital in February 2021 was selected as the study subject. Clinical data of the patient was collected, and whole exome sequencing (WES) was carried out to screen pathogenic variants associated with the phenotype. Candidate variant was validated by Sanger sequencing of her family members.@*RESULTS@#The child had normal skin, but right ear defect, hemivertebral deformity, ventricular septal defect, arterial duct and patent foramen ovale, and separation of collecting system of the left kidney. Cranial MRI showed irregular enlargement of bilateral ventricles and widening of the distance between the cerebral cortex and temporal meninges. Genetic testing revealed that she has harbored a heterozygous variant of NM_178014.4: c.217A>G (p.Met73Val) in the TUBB gene, which was unreported previously and predicted to be likely pathogenic based on the guidelines from the American College of Medical Genetics and Genomics (ACMG). The child was diagnosed with Complex cortical dysplasia with other brain malformations 6 (CDCBM6).@*CONCLUSION@#CDCBM is a rare and serious disease with great genetic heterogeneity, and CDCBM6 caused by mutations of the TUBB gene is even rarer. Above finding has enriched the variant and phenotypic spectrum of the TUBB gene, and provided important reference for summarizing the genotype-phenotype correlation of the CDCBM6.
الموضوعات
Humans , Child , Female , Abnormalities, Multiple , Blood Group Antigens , Family , Malformations of Cortical Development/genetics , Brain , Mutationالملخص
<p><b>OBJECTIVE</b>To determine the origin of chromosomal aberration for a child featuring multiple malformation, and to correlate the genotype with phenotype.</p><p><b>METHODS</b>Routine G-banding was performed to analyze the karyotype of the patient and her parents, and array comparative genomic hybridization (array CGH) was used for fine mapping of the aberrant region.</p><p><b>RESULTS</b>The karyotype of the child was ascertained as 46,XY. Array CGH has mapped a 14.21 Mb deletion to 5p15.2p15.33, and a very small 3.67 Mb duplication to 5q35.3. The patient has presented features such as mental retardation, heart defect, low-set ears, hypertelorism and down-slanting palpebral fissures.</p><p><b>CONCLUSION</b>Chromosome 5 copy number variation can cause multiple malformation. In contrast to routine karyotype analysis, array CGH can map aberrant region with much higher resolution and accuracy.</p>