Copy number variants at 4q31.3 affecting the regulatory region of FBXW7 associated with neurodevelopmental delay

Emerging research has demonstrated that genomic alterations disrupting topologically associated domains (TADs) and chromatin interactions underlie the pathogenic mechanisms of specific copy number variants (CNVs) in neurodevelopmental disorders. We report two patients with a de novo deletion and a duplication in chromosome 4q31, potentially causing FBX-related neurodevelopmental syndrome by affecting the regulatory region of FBXW7. High-throughput chromosome conformation capture (Hi-C) analysis using available capture data in neural progenitor cells revealed the rewiring of the TAD boundary close to FBXW7. Both patients exhibited facial dysmorphisms, cardiac and limb abnormalities, and neurodevelopmental delays, showing significant clinical overlap with previously reported FBXW7-related features. We also included an additional 10 patients with CNVs in the 4q31 region from the literature and the DECIPHER database for Hi-C analysis, which confirmed that disruption of the regulatory region of FBXW7 likely contributes to the developmental defects observed in these patients.

Prenatal Diagnosis of Combined Maternal 4q Interstitial Deletion and Paternal 15q Microduplication

The 4q deletion syndrome is a well-known rare genetic condition caused by partial, terminal, or interstitial deletion in the long arm (q) of chromosome 4. The phenotype of this syndrome shows a broad spectrum of clinical manifestations due to the great variability in the size and location of the deletion. In the literature, the mostly terminal deletions of chromosome 4q and the relative phenotypes are described, while the interstitial deletions of the long arm of chromosome 4 are rarely cited. Here, we report on a female fetus presenting no abnormal ultrasound evidence but with multiple chromosome aberrations. Comparative genomic hybridization (aCGH) revealed an interstitial 10.09 Mb deletion at the chromosome at the region of 4q28, arr[hg19] 4q28.1q28.3 (124068262_134158728)x1 combined with a 386.81 Kb microduplication at chromosome 15q11.1, arr[hg19] 15.11 (20249932_20636742)x3. At birth, and after 11 months, the baby was confirmed healthy and normal. The identification of this case allows for a deeper understanding of 4q syndrome and provides an explanation for the wide genetic/phenotypic spectrum of this pathology. This report can provide a reference for prenatal diagnosis and genetic counseling in patients who have similar cytogenetic abnormalities, and underlines the importance of reporting unusual variant chromosomes for diagnostic genetic purposes.

Prenatal diagnosis of a maternal 7.22-Mb deletion at chromosome 4q32.2q32.3 by SNP array

Background

Although Chromosomal microarray analysis (CMA) is a powerful diagnostic technology for detecting chromosomal copy number variants (CNVs), it detects numerous variants of unknown significance (VUSs), which poses a great challenge for genetic counselling. Terminal deletion of the long arm of chromosome 4 is a rare genetic aberration. Few cases of interstitial deletion sharing the common deleted segment have been reported.

Case presentation

A male foetus with a 7.22-Mb deletion at chromosome 4q32.2q32.3 was found in the proband. The paternal genotype was normal. His asymptomatic mother with a normal phenotype and intelligence was found to carry the same deletion at the long arm of chromosome 4. The clinical significance of arr[GRCh37] 4q32.2q32.3(162858958_170081268)×1 remains uncertain. To the best of our knowledge, this is the first case report on a VUS of 4q32 deletion and the second report of a heterochromatic CNV involving part of the long arm of chromosome 4 in a phenotypically normal mother and child. The identification of this case contributes to additional understanding of deletion at 4q32.2q32.3. This report may provide a reference for prenatal diagnosis and genetic counselling in patients who have genotypes of similar cytogenetic abnormalities.

Conclusions

The novel 7.22-Mb deletion at chromosome 4q32.2q32.3 (162858958-170081268) is a VUS. The foetus inherited this VUS from a phenotypically normal mother.

Interstitial 4q Deletion Syndrome Including NR3C2 Causing Pseudohypoaldosteronism

Interstitial and terminal deletions of chromosome 4q have been described for many years and have variable phenotypes depending on the size of the deletion present. Clinical features can include developmental delay, growth difficulty, digital differences, dysmorphic features, and cardiac anomalies. Here, we present an infant with pseudohypoaldosteronism found to have a deletion of 4q31.21q31.23, including NR3C2. Heterozygous mutations in NR3C2 have been reported to cause autosomal dominant pseudohypoaldosteronism type 1 (PHA1A). This represents a rare case of PHA1A due to a contiguous interstitial deletion and highlights the importance of evaluating patients with overlapping deletions for PHA1A.

Prenatal Diagnosis of 4q Terminal Deletion and Review of the Literature

Terminal deletion of chromosome 4 (4q deletion syndrome) is a rare genetic condition that is characterized by a broad clinical spectrum and phenotypic variability. Diagnosis of the distinct condition can be identified by conventional chromosome analysis and small deletions by novel molecular cytogenetic methods such as microarray comparative genome hybridization (aCGH). Prenatal diagnosis is challenging; to date 10 cases have been described. We report a prenatally diagnosed case of de novo 4q deletion syndrome confirmed by conventional karyotyping and FISH due to an elevated combined risk for Down syndrome and prenatal ultrasound findings. aCGH validated the diagnosis and offered exact characterization of the disorder. Cytogenetic and microarray results described a 4q32.1qter terminal deletion of the fetus. Prenatal ultrasound detected multiple nonstructural findings (micrognathia, choroid plexus cysts, echogenic fetal bowel, short femur, and cardiac axis deviation). Pregnancy was terminated at 20 weeks. In addition to the index patient, we reviewed the 10 prenatally published cases of 4q deletion syndrome in the literature and compared these with our results. We summarize the patients' characteristics and prenatal clinical findings. Alterations of maternal serum biochemical factors, an elevated combined risk for trisomies, and distinct ultrasonographic findings can often be observed in cases of prenatal 4q deletion syndrome and may facilitate the otherwise difficult prenatal diagnosis.