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This article discusses a study that aims to demonstrate the scientific validity of a novel cell-based non-invasive prenatal testing (cbNIPT) method for detecting fetal copy number variants (CNVs) using single cell sequencing of circulating extravillous trophoblasts (cEVTs). The study enrolled 1388 high-risk pregnancies and found a screen positive rate of 18.9% for aneuploidies and 11.2% for pCNVs. The results showed that cbNIPT was able to detect pCNVs <1 Mb in size, which is below the resolution of cell-free DNA screening. The authors conclude that analyzing cEVTs from maternal blood could significantly reduce the residual risk for pCNVs in early gestational weeks. [Extracted from the article]

Prenatal testing has been moving towards non-invasive methods to determine fetal risk for genetic disorders. Numerous studies have focused the attention on common trisomies; although the detection rate (DR) for trisomy 21 is high (over 95%), the accuracy regarding the DR for trisomies 13 and 18 has come under scrutiny. The testing has been applied to sex chromosome aneuploidies, but many studies have shown that it is not as effective as it is for common trisomies. Although non-invasive prenatal test (NIPT) has become a standard screening procedure for all pregnant women, invasive sampling procedures remain important in confirming NIPT-positive findings. In the present study, we report discordant results of Turner syndrome (TS) mosaicism between NIPT and karyotyping. A 35-year-old pregnant woman underwent NIPT, and a probable risk for Xp deletion was indicated. Subsequently, amniocentesis was performed. The karyotype was identified as mos 45,X [28]/46,X,i(X)(q1.0)[5]. In the second case, a 33-year-old woman underwent amniocentesis after a positive NIPT that indicated a probable risk for monosomy X. The result was mos 45,X [8]/46,XY[8]. Since NIPT is a screening test, the possibility of false-positive or false-negative results should always be considered. We underline the importance of pre/post detailed counseling. Furthermore, women with abnormal NIPT results should undergo immediate amniocentesis that remains the only tool for a correct diagnosis of sex chromosome aneuploidies., (©Carol Davila University Press.)

Microtubules participate in fundamental cellular processes, including chromosomal segregation and cell division, migration and intracellular trafficking. Their proper function is required for correct central nervous system development and operative preservation, and mutations in genes coding tubulins, the constituting units of microtubules, underlie a family of neurodevelopmental and neurodegenerative diseases, collectively known as 'tubulinopathies', characterized by a wide range of neuronal defects resulting from defective proliferation, migration and function. Here, we causally link a previously unreported missense mutation in TUBB2A (c.1249G>A, p.D417N), encoding one of the neuron-specific β-tubulin isotype II, to a disorder characterized by progressive spastic paraplegia, peripheral sensory-motor polyneuropathy and ataxia. Asp417 is a highly conserved solvent-exposed residue at the site mediating binding of kinesin superfamily motors. Impaired binding to KIF1A, a neuron-specific kinesin required for transport of synaptic vesicle precursors of the disease-associated TUBB2A mutant, was predicted by structural analyses and confirmed experimentally in vitro. We show that overexpression of TUBB2AD417N disrupts the mitotic spindle bipolarity and morphology and affects the M phase entry and length. Differently from the TUBB2AN247K and TUBB2AA248V, two mutants previously identified to affect neurodevelopment, TUBB2AD417N retains the ability to assemble into microtubules. Consistent with the differential clinical and structural impact, TUBB2AA248V does not drastically affect TUBB2A binding to KIF1A, nor mitotic spindle bipolarity. Overall, our data demonstrate a pathogenic role of the p.D417N substitution that is different from previously reported TUBB2A mutations and expand the phenotypic spectrum associated with mutations in this gene.

Pallister-Killian syndrome (PKS-#OMIM601803) is a multisystem developmental disorder typically due to the presence of an aneuploidy cell line, consisting of a supernumerary tetrasomic chromosomal marker (SCM) arisen from the short arm of chromosome 12 (12p isochromosome). The clinical phenotype, which is strictly related to the percentage and tissue distribution of aneuploid cells, is characterized by craniofacial dysmorphisms, pigmentary skin anomalies, limb shortening, congenital heart defects, diaphragmatic hernia, hypotonia, intellectual disability, and epilepsy. We report on a 4 year-old girl harboring a 12p partial isochromosome, involving the PKS critical region, affecting about 70% of circulating lymphocytes, urine, and saliva cells and fibroblast from a hyperpigmented skin spot, and 100% of fibroblasts from a hypopigmented skin spot. Interestingly, despite the high proportion of affected cells this patient did not present with PKS, and a pattern of linear and patchy pigmentary mosaicism was the sole clinical manifestation. The present observation suggests that partial 12p SCM can also result in mild phenotypes, and its prevalence in the human population could have been underestimated. Accurate dermatologic evaluation could be a major handle for genetic testing., (© 2017 Wiley Periodicals, Inc.)

Nuclear integrity and mechanical stability of the nuclear envelope (NE) are conferred by the nuclear lamina, a meshwork of intermediate filaments composed of A- and B-type lamins, supporting the inner nuclear membrane and playing a pivotal role in chromatin organization and epigenetic regulation. During cell senescence, nuclear alterations also involving NE architecture are widely described. In the present study, we utilized induced pluripotent stem cells (iPSCs) upon prolonged in vitro culture as a model to study aging and investigated the organization and expression pattern of NE major constituents. Confocal and four-dimensional imaging combined with molecular analyses, showed that aged iPSCs are characterized by nuclear dysmorphisms, nucleoskeletal components (lamin A/C-prelamin isoforms, lamin B1, emerin, and nesprin-2) imbalance, leading to impaired nucleo-cytoplasmic MKL1 shuttling, actin polymerization defects, mitochondrial dysfunctions, SIRT7 downregulation and NF-kBp65 hyperactivation. The observed age-related NE features of iPSCs closely resemble those reported for premature aging syndromes (e.g., Hutchinson-Gilford progeria syndrome) and for somatic cell senescence. These findings validate the use of aged iPSCs as a suitable cellular model to study senescence and for investigating therapeutic strategies aimed to treat premature aging.

Complex chromosomal rearrangements (CCRs) are structural aberrations involving more than 2 chromosomal breakpoints. They are associated with different outcomes depending on the deletion/duplication of genomic material, gene disruption, or position effects. Balanced CCRs can also undergo missegregation during meiotic division, leading to unbalanced derivative chromosomes and, in some cases, to affected offspring. We report on a patient presenting with developmental and speech delay, growth retardation, microcephaly, hypospadias, and dysmorphic features, harboring an interstitial 10q21.1q23.31 duplication, due to recombination of a paternal CCR. Application of several cytogenetic and molecular techniques allowed determining the biological bases of the rearrangement, understanding the underlying chromosomal mechanism, and assessing the reproductive risk., (© 2017 S. Karger AG, Basel.)