From phenotype to mechanism: Prenatal spectrum of NKAP mutation-related disorder and its pathogenesis inducing congenital heart disease.

NKAP mutations are associated with Hackmann-Di Donato-type X-linked syndromic intellectual developmental disorder (MRXSHD, MIM: #301039). Here, we elucidate the potential prenatal manifestation of NKAP mutation-associated disorder for the first time, alongside revealing the relationship between NKAP mutations and congenital heart defect (CHD) in the Chinese population. An NKAP mutation (NM_024528.4: c.988C>T, p.Arg330Cys) was identified in two foetuses presenting with CHD. Subsequent mechanistic exploration revealed a marked downregulation of NKAP transcription within HEK293T cells transfected with NKAP p.R330C. However, no significant change was observed at the protein level. Moreover, the mutation led to a dysregulation in the transcription of genes associated with cardiac morphogenesis, such as DHRS3, DNAH11 and JAG1. Additionally, our research determined that NKAP p.R330C affected Nkap protein intra-nuclear distribution, and binding with Hdac3. Summarily, our study strengthens NKAP mutations as a cause of CHD and prompts the reclassification of NKAP p.R330C as likely pathogenic, thereby establishing a prospective prenatal phenotypic spectrum that provides new insight into the prenatal diagnosis of CHD. Our findings also provide evidence of NKAP p.R330C pathogenicity and demonstrate the potential mechanism by which p.R330C dysregulates cardiac developmental gene transcription by altering Nkap intra-nuclear distribution and obstructing the interaction between Nkap and Hdac3, thereby leading to CHD.

Clinical Characteristics and Molecular Genetic Analysis of a Pedigree with Glanzmann's Thrombasthenia.

Objective: The objective of this study was to investigate the clinical phenotype and genetic etiology of Glanzmann's thrombasthenia in a consanguineous pedigree. Methods: Clinical data and ancillary test results were collected from pedigrees with Glanzmann's thrombasthenia. High-throughput sequencing was used to detect variants in the proband. Candidate variants were verified by Sanger sequencing. Results: Two patients in the pedigree were homozygous for the c.2248C>T (p. Arg750Ter) variant of the ITGB3 gene. The parents and maternal grandmother, who didn't have any recurrent haemorrhage, were found to carry a heterozygous c.2248C>T variant of the ITGB3 gene, which was absent in the aunt and paternal grandmother. Conclusion: The homozygous variant c.2248C>T (p. Arg750Ter) in the ITGB3 gene underlies the disease in this pedigree. This diagnosis will facilitate genetic counselling in this pedigree for better patient management and life guidance.

[Application of chromosomal microarray analysis for fetuses with choroid plexus cysts].

OBJECTIVE: To assess the value of chromosomal microarray analysis (CMA) for fetuses with choroid plexus cysts (CPC) detected by prenatal ultrasonography. METHODS: Amniotic fluid chromosomal karyotype was analyzed in 104 fetuses with CPC, and copy number variations (CNVs) among the fetuses were detected by using CMA. RESULTS: Ten fetuses (9.62%) were found to have an abnormal karyotype, and 14 additional CNVs were detected in those with a normal karyotype. The fetuses were divided into isolated CPC group (n = 87) and non-isolated CPC group (n = 17) based on the presence of additional ultrasonographic abnormalities. The detection rates for karyotypic abnormalities of the two groups were 4.6% and 35.3%, respectively, whilst those for the CMA were 4.6% and 47.1%, respectively. The detection rates for karyotypic abnormalities and CMA of the non-isolated CPC group were significantly higher than those of the isolated CPC group (P < 0.05). The detection rate for CMA in the non-isolated group was significantly higher than chromosomal karyotype abnormalities (P < 0.05). Among the 8 fetuses with abnormal CMA, 4 had single umbilical artery, 3 had abnormal cardiac structure, and 2 had enhanced intestinal echo. CONCLUSION: CPC is closely associated with chromosomal abnormalities. Chromosome karyotype analysis in combination with CMA can effectively detect fetal chromosomal abnormalities and provide a basis for genetic counseling.

[Value of non-invasive prenatal testing for the detection of fetal chromosomal copy number variations].

OBJECTIVE: To explore the value of non-invasive prenatal testing (NIPT) for the detection of fetal chromosome copy number variations (CNVs). METHODS: Clinical data of 18 661 pregnant women who underwent NIPT were collected. For fetuses suspected for carrying CNVs, amniotic fluid samples were collected for chromosomal karyotyping and/or chromosomal microarray analysis (CMA). RESULTS: Among all samples, NIPT suggested that 58 fetuses carried trisomy 21, 18 carried trisomy 18, 19 carried trisomy 13, 1 carried trisomies 18 and 21. Eighty eight women accepted invasive prenatal diagnosis. The results of CMA in 59 cases were consistent with those of NIPT, which yielded a consistency rate of 67.05%. In addition, 37 cases of fetal CNVs were detected by NIPT, of which 19 (15 microdeletions and 4 microduplications) have accepted invasive prenatal diagnosis. In 14 cases, the results were consistency with those of NIPT, with a consistent rate of 73.68%. CONCLUSION: NIPT features high sensitivity and accuracy. Invasive prenatal diagnosis should be considered for CNVs detected by NIPT, and by tracing its parental origin, it can provide guidance for clinical practice.

A Novel External Quality Assessment of Chromosomal Karyotype Analysis Based on Chimera Image Assembly.

OBJECTIVE: This study aimed to establish a new external quality assessment (EQA) of chromosomal karyotype analysis. METHODS: Chimeric assembly A1 was established by collecting chimeric chromosome images prepared artificially from chromosomally abnormal amniocytes remaining after prenatal diagnosis. Chimeric assembly B1 and nonchimeric assembly C1 were constructed through the collection of chimeric and nonchimeric chromosome images from prenatal diagnosis, respectively. Then, chromosome images were selected randomly from assemblies A1, B1, or C1 to send to 20 technicians via email to verify the validity of a new EQA of chromosomal karyotype analysis. RESULTS: According to the EQA of 20 technicians, 47,XX,+mar from assembly A was easily misdiagnosed as 47,XX,+19 or 47,XXY, and 45,XX,t(13;22) (q10;q10) was misdiagnosed as 45,XX,13S+,-22. The total misdiagnosis rate was 3.8%. For assembly B, 46,X,+mar and 46,X,idic(Y) were easily misdiagnosed as 46,XY and 46,X,+mar, respectively. In addition, some testers missed 47,XXX in 47,XXX[2]/46,XX[48], as well as 47,XX,+18 in 46,XX [47]/47,XX,+18[3], and 45,X and 47,XXX in 46,XX[47]/45,X[2]/47,XXX[1]. The total misdiagnosis rate was 4.2%. All karyo-types from assembly C were correctly diagnosed, although incorrect descriptions used for 4% of cases. CONCLUSION: The quality of chromosome karyotype analysis can be comprehensively evaluated by a new EQA based on assembly A1 or B1.