Rare form of autosomal dominant familial Cornelia de Lange syndrome due to a novel duplication in SMC3

Identification of two novel heterozygous variants of SMC3 with Cornelia de Lange syndrome

BACKGROUND

Cornelia de Lange syndrome (CdLS) is a multisystem genetic disorder, and cases caused by variants in the structural maintenance of chromosomes protein 3 (SMC3) gene are uncommon. Here, we report two cases of CdLS associated with novel pathogenic variants in SMC3 from two Chinese families.

METHODS

Clinical presentations of two patients with CdLS were evaluated, and specimens from the patients and other family members were collected for Trio-based whole-exome sequencing. Pyrosequencing, chip-based digital PCR, minigene splicing assay, and in silico analysis were carried out to elucidate the impact of novel variants.

RESULTS

Novel heterozygous variants in SMC3 were identified in each proband. One harbored a novel splicing and mosaic variant (c.2535+1G>A) in SMC3. The mutated allele G>A conversion was approximately 23.1% by digital PCR, which indicated that 46.2% of peripheral blood cells had this variant. Additionally, in vitro minigene splicing analysis validated that the c.2535+1G>A variant led to an exon skipping in messenger RNA splicing. The other carried a heterozygous variant (c.435C>A), which was predicted to be pathogenic as well as significantly altered in local electrical potential. The former showed multiple abnormalities and marked clinical severity, and the latter mainly exhibited a speech developmental disorder and slightly facial anomalies.

CONCLUSION

Both patients were clinically diagnosed with Cornelia de Lange syndrome 3 (CdLS3). The newly identified SMC3 gene variants can expand the understanding of CdLS3 and provide reliable evidence for genetic counseling to the affected family.

A novel de novo HDAC8 missense mutation causing Cornelia de Lange syndrome

Background

Cornelia de Lange syndrome (CdLS) is a rare and clinically variable syndrome characterized by growth impairment, multi‐organ anomalies, and a typical set of facial dysmorphisms. Here we describe a 2‐year‐old female child harboring a novel de novo missense variant in HDAC8, whose phenotypical score, according to the recent consensus on CdLS clinical diagnostic criteria, allowed the diagnosis of a non‐classic CdLS.

Methods

Clinical exome sequencing was performed on the trio, identifying a de novo heterozygous variant in HDAC8 (NM_018486; c. 356C>G p.Thr119Arg). Molecular modeling was performed to evaluate putative functional consequence of the HDAC8 protein.

Results

The variant HDAC8 c.356C>G is classified as pathogenic following the ACMG (American College of Medical Genetics and Genomics)/AMP (Association for Molecular Pathology) guidelines. By molecular modeling, we confirmed the deleterious effect of this variant, since the amino acid change compromises the conformational flexibility of the HDAC8 loop required for optimal catalytic function.

Conclusion

We described a novel Thr119Arg mutation in HDAC8 in a patient displaying the major phenotypic traits of the CdLS. Our results suggest that a modest change outside an active site is capable of triggering global structural changes that propagate through the protein scaffold to the catalytic site, creating de facto haploinsufficiency.

A Chinese Case of Cornelia de Lange Syndrome Caused by a Pathogenic Variant in SMC3 and a Literature Review

PURPOSE

Cornelia de Lange syndrome (CdLS) is a rare congenital developmental disorder, and cases caused by variants in SMC3 are infrequent. This article describes a case of CdLS related to a pathogenic variant in SMC3 and performs a literature review.

METHODS

We collected clinical data and biological samples from a 12-year-old boy with "short stature for 11 years". Gene variants in the proband were detected by whole-exome sequencing, and the variants in his parents were verified by Sanger sequencing. All SMC3-related CdLS patients from the PubMed and Web of Science databases were collected and summarized using the available data.

RESULTS

A pathogenic variant in SMC3 in the proband, c.1942A>G, was identified. Neither of his parents carried the same variant. Twenty-eight patients were diagnosed with CdLS with variants in SMC3, including the cases in this study and those reported in the literature, where half of the variant types were missense, followed by 32% (9/28) with a deletion and 11% (3/28) with a duplication. All patients showed symptoms of verbal development delay and intellectual disability to different degrees, and 90% patients had long eyelashes while 89% patients had arched eyebrows.

CONCLUSION

This study summarized different gene variants in SMC3 and the frequencies of the various clinical manifestations according to the reported literature. For CdLS caused by SMC3 variants, short stature and facial dysmorphic features are the two most important clinical clues. Definite diagnosis of this rare disease may be challenging clinically; thus, it is significant to use molecular diagnosis.

Parenchymal Organ Changes in Two Female Patients With Cornelia de Lange Syndrome: Autopsy Case Report

Cornelia de Lange (CdLS) is a rare congenital disorder with multifactor etiology. The syndrome features a wide variety of physical and cognitive hallmarks such as distinctive facial appearance, small stature, bone, and gastrointestinal abnormalities. Two cases of patients clinically diagnosed with CdLS are reported. Both cases were diagnosed and treated at the St. Marina University Hospital, Varna, Bulgaria and were referred for autopsy after death. The first case was of a female patient, aged 7 and the second of a 17-years-old female. Both patients had a family history, severe features, and complications associated with CdLS. In both cases, the liver had normal anatomical proportions with a slightly flattened shape especially pronounced in the second case where the liver had a pyramidal shape with sharp edges. The kidneys in both patients were with a flattened pyramidal shape, with the tip located at the hilum and a base toward the lateral abdominal side. Both patients also had a pyramidal shaped spleen, again with the tip located at the hilum, with the second patient having multiple accessory spleens along the splenic artery. The cause of death in both patients was determined as complications from CdLS. The pyramidal form of the parenchymal organs is a manifestation that has so far not been described in CdLS patients. Despite atrophic organs sometimes having the same appearance, different organs are rarely affected identically, hence these changes can be considered as specific features of CdLS.

Hydrogen gas inhibits lung cancer progression through targeting SMC3

Lung cancer is one of the most common lethal malignancies in the globe. The patients' prognoses are dim due to its high metastatic potential and drug resistance. Therefore, in the present study, we aim to find a more potent therapeutic approach for lung cancer. We mainly explored the function of hydrogen gas (H₂) on cell viability, apoptosis, migration and invasion in lung cancer cell lines A549 and H1975 by CCK-8, flow cytometry, wound healing and transwell assays, respectively. We used RNA-seq, qPCR and western blotting to detect the different expression genes (DEGs) between H₂ group and control group to find the gene related to chromosome condensation. Besides, we confirmed the structural maintenance of chromosomes 3 (SMC3) and H₂ on the progression of lung cancer in vitro and vivo. Results showed that H₂ inhibited cell viability, migration and invasion, and catalyzed cell apoptosis and H₂ induced A549 and H1975 cells G2/M arrest. Besides, H₂ down-regulated the expression of NIBPL, SMC3, SMC5 and SMC6, and also reduced the expression of Cyclin D1, CDK4 and CDK6. H₂ translocated the subcellular location of SMC3 during cell division and decreased its stability and increased its ubiquitination in both A549 and H1975 cells. In addition, inhibition of the proliferation, migration and invasion and promotion of the apoptosis of A549 and H1975 cells induced by H₂ were all abolished when overexpressed SMC3 in the presence of H₂. Animal experimental assay demonstrated that the tumor weight in H₂ group was significantly smaller than that in control group, but was bigger than cis-platinum group. The expression of Ki-67, VEGF and SMC3 were decreased when mice were treated with H₂ or cis-platinum, especially for cis-platinum. All data suggested that H₂ inhibited lung cancer progression through down-regulating SMC3, a regulator for chromosome condensation, which provided a new method for the treatment of lung cancer.