Non-Invasive Screening Tools for Down’s Syndrome: A Review

diagnostic

Rapid RHD Zygosity Determination Using Digital PCR.

BACKGROUND: Paternal zygosity testing is used for determining homo- or hemizygosity of RHD in pregnancies that are at a risk of hemolytic disease of the fetus and newborn. At present, this is achieved by using real-time PCR or the Rhesus box PCR, which can be difficult to interpret and unreliable, particularly for black African populations. METHODS: DNA samples extracted from 58 blood donors were analyzed using 2 multiplex reactions for RHD-specific targets against a reference (AGO1)(2) to determine gene dosage by digital PCR. Results were compared with serological data, and the correct genotype for 2 discordant results was determined by long-range PCR, next-generation sequencing, and conventional Sanger sequencing. RESULTS: The results showed clear and reliable determination of RHD zygosity using digital PCR and revealed that 4 samples did not match the serologically predicted genotype. Sanger sequencing and long-range PCR (LR-PCR) followed by next-generation sequencing revealed that the correct genotypes for samples 729M and 351D, which were serologically typed as R1R2 (DCe/DcE), were R2r\u27 (DcE/dCe) for 729M and R1r (DCe/dcE), R0r(y) (Dce/dCE), or RZr (DCE/dce) for 351D, in concordance with the digital PCR data. CONCLUSIONS: Digital PCR provides a highly accurate method to rapidly define blood group zygosity and has clinical application in the analysis of Rh phenotyped or genotyped samples. The vast majority of current blood group genotyping platforms are not designed to define zygosity, and thus, this technique may be used to define paternal RH zygosity in pregnancies that are at a risk of hemolytic disease of the fetus and newborn and can distinguish between homo- and hemizygous RHD-positive individuals

The proteome signatures of fibroblasts from patients with severe, intermediate and mild spinal muscular atrophy show limited overlap

Most research to characterise the molecular consequences of spinal muscular atrophy (SMA) has focused on SMA I. Here, proteomic profiling of skin fibroblasts from severe (SMA I), intermediate (SMA II), and mild (SMA III) patients, alongside age-matched controls, was conducted using SWATH mass spectrometry analysis. Differentially expressed proteomic profiles showed limited overlap across each SMA type, and variability was greatest within SMA II fibroblasts, which was not explained by SMN2 copy number. Despite limited proteomic overlap, enriched canonical pathways common to two of three SMA severities with at least one differentially expressed protein from the third included mTOR signalling, regulation of eIF2 and eIF4 signalling, and protein ubiquitination. Network expression clustering analysis identified protein profiles that may discriminate or correlate with SMA severity. From these clusters, the differential expression of PYGB (SMA I), RAB3B (SMA II), and IMP1 and STAT1 (SMA III) was verified by Western blot. All SMA fibroblasts were transfected with an SMN-enhanced construct, but only RAB3B expression in SMA II fibroblasts demonstrated an SMN-dependent response. The diverse proteomic profiles and pathways identified here pave the way for studies to determine their utility as biomarkers for patient stratification or monitoring treatment efficacy and for the identification of severity-specific treatments

Evidence for digenic inheritance in some cases of Antley-Bixler syndrome?

The Antley-Bixler syndrome has been thought to be caused by an autosomal recessive gene. However, patients with this phenotype have been reported with a new dominant mutation at the FGFR2 locus as well as in the offspring of mothers taking the antifungal agent fluconazole during early pregnancy. In addition to the craniosynostosis and joint ankylosis which are the clinical hallmarks of the condition, many patients, especially females, have genital abnormalities. We now report abnormalities of steroid biogenesis in seven of 16 patients with an Antley-Bixler phenotype. Additionally, we identify FGFR2 mutations in seven of these 16 patients, including one patient with abnormal steroidogenesis. These findings, suggesting that some cases of Antley-Bixler syndrome are the outcome of two distinct genetic events, allow a hypothesis to be formulated under which we may explain all the differing and seemingly contradictory circumstances in which the Antley-Bixler phenotype has been recognised.


Keywords: Antley-Bixler syndrome; FGFR; congenital adrenal hyperplasia; CYP21 deficienc

X linked fatal infantile cardiomyopathy maps to Xq28 and is possibly allelic to Barth syndrome

A number of families with X linked dilated cardiomyopathy with onset in infancy or childhood have now been described, with varying clinical and biochemical features. Of these, one condition, Barth syndrome (BTHS), can be diagnosed clinically by the characteristic associated features of skeletal myopathy, short stature, and neutropenia, but not all of these features are always present. Molecular genetic studies have delineated the gene for BTHS, which maps to distal Xq28, from the gene for so called X linked dilated cardiomyopathy (XLCM), a teenage onset dilated cardiomyopathy, recently mapped to the 5' portion of the dystrophin locus at Xp21. We report a large family in which male infants have died with congenital dilated cardiomyopathy, and there is a strong family history of unexplained death in infant males over at least four generations. Death always occurred in early infancy, without development of the characteristic features associated with Barth syndrome. Molecular analysis localised the gene in this family to Xq28 with lod scores of 2.3 at theta = 0.0 with dinucleotide repeat markers, p26 and p39, near DXS15 and at F8C. The proximal limit to the localisation of the gene in this family is defined by a recombinant at DXS296, while the distal limit could not be differentiated from the telomere. This localisation is consistent with a hypothesis of allelic and clinical heterogeneity at the BTHS locus in Xq28