ABSTRACT
Objective:To investigate the genetic etiology of a pedigree with autosomal recessive congenital ichthyosis.Methods:Whole-exome sequencing was performed in a collodion baby, and Sanger sequencing was conducted to verify gene mutations. The PolyPhen-2, PROVEAN and Mutation Taster softwares, as well as protein homology modeling methods, were used to predict effects of gene variants; real-time fluorescence-based quantitative PCR and Western blot analysis were performed to analyze the effect of mutations on allelic mRNA and protein expression.Results:Whole-exome sequencing and Sanger sequencing confirmed a mutation c.919C>T (p.Arg307Trp) in exon 6 and a mutation c.1019G>A (p.Gly340Glu) in exon 7 of the TGM1 gene in the infant, which were inherited from his mother and father respectively. Bioinformatics analysis suggested that both the two mutations were harmful to protein structures, which were further supported by protein homology modeling. In vitro experiments showed that there was no significant difference in the mRNA expression of the TGM1 gene between the 293T cells transfected with wild-type plasmids and those transfected with mutant plasmids containing the mutation c.919C>T or c.1019G>A ( t=1.97, 1.28, P=0.12, 0.27, respectively) , but the TGase1 protein expression significantly decreased in the 293T cells transfected with the mutant TGM1 plasmids. Conclusion:The mutations c.919C>T and c.1019G>A in the TGM1 gene may be the molecular genetic etiology of severe ichthyosis in the infant, and the missense amino acids encoded by the two mutations may affect the TGase1 protein function by destroying its structure.
ABSTRACT
OBJECTIVE@#To provide genetic counseling for a couple with recurrent detection of fetal structural abnormality during second trimester pregnancy.@*METHODS@#The fetal tissue and peripheral blood samples of the couple were subjected to G banded chromosomal analysis, copy number variation sequencing (CNV-seq) and fluorescence in situ hybridization (FISH) assays.@*RESULTS@#CNV-seq has detected a 6.59 Mb duplication at 7p22.3-p22.1 and a 3.81 Mb deletion at 4p16.3 in the fetal tissue, though conventional karyotyping results of both parents were normal. FISH has confirmed that the father has harbored a cryptic translocation of t(4;7)(7p+,4q+,4p+,7q+).@*CONCLUSION@#The ultrasonographic abnormality of the fetuses may be attributed to the 7p microduplication and 4p microdeletion derived from the cryptic translocation carried by the father. Reciprocal translocation of tiny chromosomal segments should be suspected for couples with recurrent adverse pregnancies but apparently normal karyotypes.
Subject(s)
Female , Humans , Pregnancy , Chromosome Disorders , DNA Copy Number Variations , In Situ Hybridization, Fluorescence , Karyotyping , Translocation, GeneticABSTRACT
OBJECTIVE@#To determine the size and origin of a small supernumerary marker chromosome (sSMC) identified in a patient featuring developmental retardation.@*METHODS@#High-throughput sequencing for copy number variation (CNV-seq) was carried out to delineate the sSMC identified upon G-banded chromosomal karyotyping. The genotype-phenotype correlation was explored by database retrieval and literature analysis.@*RESULTS@#The patient was found to have a karyotype of mos 47,XX,+mar[36]/46,XX[23]. CNV-seq has identified a 18 Mb duplication at 5p14.1-p12 (hg19: 27,399,261-46,083,784)x2.6 with a mosaicism rate of approximately 60%.@*CONCLUSION@#Patients with mosaic partial trisomy 5p may have extensive clinical manifestations, and the ratio of trisomy 5p cells is correlated with clinical severity of this syndrome.