A nonsense CC2D1A variant is associated with congenital anomalies, motor delay, hypotonia, and slight deformities.

Background: Autosomal recessive intellectual developmental disorder-3 is caused by homozygous or compound heterozygous mutations in the CC2D1A gene. The disorder is characterized by intellectual disability (ID) and autism spectrum disorder (ASD). To date, 39 patients from 17 families with CC2D1A -related disorders have been reported worldwide, in whom only six pathogenic or likely pathogenic loss-of-function variants and three variants of uncertain significance (VUS) in the CC2D1A gene have been identified in these patients. Methods: We described a patient with ID from a non-consanguineous Chinese family and whole-exome sequencing (WES) was used to identify the causative gene. Results: The patient presented with severe ID and ASD, speech impairment, motor delay, hypotonia, slight facial anomalies, and finger deformities. Threatened abortion and abnormal fetal movements occurred during pregnancy with the proband but not his older healthy sister. WES analysis identified a homozygous nonsense variant, c.736C > T (p.Gln246Ter), in the CC2D1A gene. In addition, six novel likely pathogenic CC2D1A variants were identified by a retrospective review of the in-house database. Conclusions: This study expands the genetic and clinical spectra of CC2D1A-associated disorders, and may aid in increasing awareness of this rare condition. Our findings have provided new insights into the clinical heterogeneity of the disease and further phenotype-genotype correlation, which could help to offer scope for more accurate genetic testing and counseling to affected families.

A genetic variant in the MAST1 gene is associated with mega-corpus-callosum syndrome with hypoplastic cerebellar vermis, in a fetus.

BACKGROUND: Mega-corpus-callosum syndrome with cerebellar hypoplasia and cortical malformations is a rare neurological disorder that is associated with typical clinical and imaging features. The syndrome is caused by pathogenic variants in the MAST1 gene, which encodes a microtubule-associated protein that is predominantly expressed in postmitotic neurons in the developing nervous system. METHODS: Fetal DNA from umbilical cord blood samples and genomic DNA from peripheral blood lymphocytes were subjected to whole-exome sequencing. The potential causative variants were verified by Sanger sequencing. RESULTS: A 26-year-old primigravid woman was referred to our prenatal center at 25 weeks of gestation due to abnormal ultrasound findings in the brain of the fetus. The brain abnormalities included wide cavum septum pellucidum, shallow and incomplete bilateral lateral fissure cistern, bilateral dilated lateral ventricles, hyperplastic corpus callosum, lissencephaly, and cortical dysplasia. No obvious abnormalities were observed in the brainstem or cerebellum hemispheres, but the cerebellum vermis was small. Whole-exome sequencing identified a de novo, heterozygous missense variant, c.695T>C(p.Leu232Pro), in the MAST1 gene and a genetic diagnosis of mega-corpus-callosum syndrome was considered. CONCLUSION: This study is the first prenatal case of MAST1-related disorder reported in the Chinese population and has expanded the mutation spectrum of the MAST1 gene.

[Application of flat-sided culture tubes during prenatal diagnosis].

OBJECTIVE: To assess the value of using flat-sided culture tubes for preparing chromosomes through chorionic villi (CV) and amniotic fluid (AF) cell cultures during prenatal diagnosis. METHODS: From February to March 2020, 157 CV samples and 147 AF samples subjected to prenatal diagnosis at the Maternal and Child Health Care Hospital of Guangxi Zhuang Autonomous Region were selected as the study subjects. For each sample, one flat-sided tube and one flask culture were set up by following the standard protocols. The methods were evaluated by comparing the cell growth, experimental process, quality of chromosome preparation and costs. RESULTS: The success rates for the culturing of CV and AF samples by the flat-sided culture tube method were 97.45% (153/157) and 97.96% (144/147), respectively. By contrast, the success rates for the conventional flask method were 98.72% (155/157) for CV and 98.64% (145/147) for AF samples. No significant difference was found between the two methods (P > 0.05). The average harvest time required by the flat-sided culture tube method was 8.45 days for CV and 9.43 days for AF cultures, whilst the average harvest time for conventional flask method was 9.05 days and 9.54 days, respectively. The flat-sided culture tube method for CV had required significantly shorter average harvest time than the conventional method (P < 0.001). No statistical significant difference was found in the average harvest time for AF by the two methods (P > 0.05). The conventional culturing method had required three containers with two sample transfers. By contrast, the flat-sided culture tube method was carried out in one tube without any sample transfer. The average total amount of medium used was 3.91 mL for each flat-sided culture tube and 6.26 mL for each conventional flask. CONCLUSION: The flat-sided culture tube method can provide a simple, cost-effective and error-reducing procedure for the CV and AF samples culture during prenatal diagnosis.