Characterization of RHD locus polymorphism in D negative and D variant donors from northwestern Argentina

A notable RHD variability has been observed in Central Argentina's current population attributed to the intermixing of different ethnic groups. The Northwestern region of the country is characterized by a markedly Amerindian genetic contribution. In this sense, the definition of the RHD polymorphism in individuals from this area was lacking. A total of 757 donors from Northwestern Argentina, with D negative C and/or E positive (n = 526), and D variant (n = 231) phenotype defined by standard hemmaglutination tube techniques were genotyped using in-house PCR strategies, commercial SNP arrays and Sanger sequencing. RESULTS Among D negative C and/or E positive samples, RHD null (15.40%) and DEL alleles (3.23%) were identified. One unreported SNP c.1001T>A responsible for a null allele was found. RHD*01N.75 (4.18%) and RHD*DEL43 (2.66%) were the most prevalent variants following RHD*03N.01 (8.75%). The characterization of serologic weak D phenotypes showed that RHD*weak D type 1, 2, and 3 variants were found only in 37.24% of the samples, whereas RHD*weak D type 93 was the most prevalent allele (25.11%). Also, a previously unreported missense variation c.764G>A was identified. A RHD genotyping strategy for patients and donors from Northwestern Argentina must consider the detection of the frequently found RHD*01N.75, RHD*DEL43, and RHD*weak D type 93 variants. Taking into account that RHD*DEL43 has scarcely been found in North Americans and Europeans whereas RHD*01N.75 and RHD*weak D type 93 have never been described in populations other than Argentineans, these RHD variants could be attributed to Native Amerindian genetic influence591032363242FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPnão temThis work was supported in part by a grant from the Agencia Nacional de Promoción Científica y Tecnológica (Project: PICT 2015‐2324), Argentina. Funding was also received from CONICET (Argentina) and FAPESP (Brazil

Unexpected relevant role of gene mosaicism in patients with primary immunodeficiency diseases

BACKGROUND: Postzygotic de novo mutations lead to the phenomenon of gene mosaicism. The 3 main types are called somatic, gonadal, and gonosomal mosaicism, which differ in terms of the body distribution of postzygotic mutations. Mosaicism has been reported occasionally in patients with primary immunodeficiency diseases (PIDs) since the early 1990s, but its real involvement has not been systematically addressed. OBJECTIVE: We sought to investigate the incidence of gene mosaicism in patients with PIDs. METHODS: The amplicon-based deep sequencing method was used in the 3 parts of the study that establish (1) the allele frequency of germline variants (n = 100), (2) the incidence of parental gonosomal mosaicism in families with PIDs with de novo mutations (n = 92), and (3) the incidence of mosaicism in families with PIDs with moderate-to-high suspicion of gene mosaicism (n = 36). Additional investigations evaluated body distribution of postzygotic mutations, their stability over time, and their characteristics. RESULTS: The range of allele frequency (44.1% to 55.6%) was established for germline variants. Those with minor allele frequencies of less than 44.1% were assumed to be postzygotic. Mosaicism was detected in 30 (23.4%) of 128 families with PIDs, with a variable minor allele frequency (0.8% to 40.5%). Parental gonosomal mosaicism was detected in 6 (6.5%) of 92 families with de novo mutations, and a high incidence of mosaicism (63.9%) was detected among families with moderate-to-high suspicion of gene mosaicism. In most analyzed cases mosaicism was found to be both uniformly distributed and stable over time. CONCLUSION: This study represents the largest performed to date to investigate mosaicism in patients with PIDs, revealing that it affects approximately 25% of enrolled families. Our results might have serious consequences regarding treatment and genetic counseling and reinforce the use of next-generation sequencing-based methods in the routine analyses of PIDs.status: publishe