NUP188 Biallelic Loss of Function May Underlie a New Syndrome: Nucleoporin 188 Insufficiency Syndrome?

There is no clearly established association between the gene NUP188 and human pathology. Only a few reports of patients with different clinical presentation and different heterozygous or compound heterozygous missense or splice region variants have been identified in several sequencing projects; however, a causative association between the clinical features and the identified variants has not been established. For the first time, we report 2 unrelated patients with 2 different homozygous nonsense gene variants of NUP188, p.Tyr96* and p.Gln113*, respectively. Although having different supposedly truncating mutations, the patients presented with strikingly comparable phenotypes including pre- and postnatal microcephaly, trigonocephaly, congenital bilateral cataract, microphthalmia, cleft lip and palate or high-arched palate, camptodactyly, rocker-bottom feet, heart anomalies, specific brain changes (such as loss of periventricular white matter), thin corpus callosum, and delayed myelinization. Both patients showed very similar facial features such as laterally extended arched eyebrows, wide convex nose with a wide prominent nasal bridge, and prominent angulated antihelix. They were both born small for gestational age and died shortly after birth at the age of 67 and 140 days, respectively, as a result of central respiratory failure. Our findings strongly suggest a correlation between the homozygous nonsense gene variants of NUP188 and a severe phenotype of a new developmental syndrome with poor prognosis resulting from nucleoporin 188 homolog protein insufficiency.

Novel SMAD3 p.Arg386Thr genetic variant co-segregating with thoracic aortic aneurysm and dissection.

BACKGROUND: Pathogenic variants in the SMAD3 gene affecting the TGF-ß/SMAD3 signaling pathway with aortic vessel involvement cause Loeys-Dietz syndrome 3, also known as aneurysms-osteoarthritis syndrome. METHODS: Description of clinical history of a family in Sweden using clinical data, DNA sequencing, bioinformatics, and pedigree analysis. RESULTS: We report a novel SMAD3 variant, initially classified as a genetic variant of uncertain clinical significance (VUS), and later found to be co-segregating with aortic dissection in the family. The index patient presented with a dissecting aneurysm of the aorta including the ascending, descending, and abdominal parts. Genotype analysis revealed a heterozygous missense SMAD3 variant: NM_005902.3(SMAD3): c.11576G > C (p.Arg386Thr). The same variant was also identified in a 30 years old formalin-fixed paraffin-embedded block of tissue from a second cousin, who died at 26 years of age from a dissecting aneurysm of the aorta. CONCLUSION: A "variant of uncertain significance" according to the ACMG guidelines has always a scope for reappraisal. Genetic counselling to relatives, and the offering of surveillance service is important to families with aortic aneurysm disease. The report also highlight the potential use of FFPE analysis from deceased relatives to help in the interpretation of variants.