Novetats en el diagnòstic genètic preimplantacional

La tesi doctoral d'Aïda Pujol ha estudiat una variant del diagnòstic genètic preimplantacional en la fecundació in vitro. Va analitzar la irregularitat numèrica dels cromosomes en els oòcits i en el desenvolupament embrionari mitjançant la hibridació in situ fluorescent (FISH). Gràcies a això va poder indentificar els diferents mecanismes que produeixen aquesta anomalia.La tesis doctoral de Aida Pujol ha estudiado una variante del diagnóstico genético preimplantacional en la fecundación in vitro. Analizó la irregularidad numérica de los cromosomas en los ovocitos y el desarrollo embrionario mediante hibridación in situ fluoroscente (FISH). Gracias a ello pudo identificar los diferentes mecanismos que producen esta anomalía

Anàlisi citogenètica preimplantacional : alteracions cromosòmiques numèriques i estructurals /

Consultable des del TDXTítol obtingut de la portada digitalitzadaL'anàlisi citogenètica del 1er corpuscle polar (1CP) permet una caracterització indirecta de l'oòcit en metafase II (MII) sense comprometre la seva capacitat reproductiva. Això permet, dins un programa de fecundació in vitro (FIV), desenvolupar una variant del diagnòstic genètic preimplantacional en la que s'analitza el 1CP (DGP-1CP). L'objectiu general d'aquest treball és estudiar la incidència d'aneuploïdia en la línia germinal femenina i en els primers estadis del desenvolupament embrionari. S'han utilitzat oòcits descartats de cicles de FIV per a desenvolupar una metodologia de hibridació in situ fluorescent (FISH) que permet detectar nou cromosomes en 1CPs i en MII. Fins ara, les absències de cromosomes o cromàtides en 1CP es consideraven artefactes però la valoració de la complementarietat 1CP- MII realitzada constata que només ho són una minoria (25,8%). Tant la freqüència d'aneuploïdia obtinguda per als nou cromosomes estudiats (47,5%) com el risc estimat d'aneuploïdia per els 23 cromosomes (57,2%) són molt elevats. El risc estimat de segregació anòmala per cromosoma analitzat és del 0,89%. S'han identificat diferents mecanismes de generació d'aneuploïdies en l'oòcit: separació precoç de cromàtides germanes (observada amb més freqüència al 1CP que a la MII) i no-disjunció de cromosomes homòlegs en la meiosi i segregació anòmala en la mitosi de l'etapa proliferativa de la línia germinal (mosaïcisme gonadal). Aquest fenomen s'ha detectat en un 25,7% de les pacients analitzades i fa recomanable el diagnòstic prenatal a les pacients que quedin gestants després d'un DGP-1CP. Aplicant DGP-1CP a dones amb cariotip normal (dones d'edat avançada), la incidència d'aneuploïdia per als nou cromosomes ha estat del 60,4%, corroborant a aquest grup com a grup de risc per la presència d'aneuploïdies. Aplicant-lo a dues pacients portadores de translocacions robertsonianes s'ha trobat una taxa d'aneuploïdia molt alta per als cromosomes no implicats en la translocació (91,7% i 72,7%), independentment de les alteracions observades per als cromosomes de la translocació. L'anàlisi d'aneuploïdies en blastòmers de pacients portadors i portadores de translocacions recíproques mostra un alt índex d'aneuploïdies de cromosomes no implicats en la translocació (60,3%) i també un alt percentatge de mosaïcisme (58,7%), tenint en compte tant els cromosomes implicats com els no implicats en la translocació. S'han trobat embrions normals o equilibrats per la translocació però aneuploides per altres cromosomes. Sembla necessari l'estudi seqüencial de la segregació dels cromosomes implicats en la translocació i de les aneuploïdies per altres cromosomes, en pacients portadors de translocacions. Per a validar la interpretació del resultat de la FISH en l'anàlisi d'aneuploïdia en cèl·lules proliferants, s'han estudiat cèl·lules en estadi de G0 (cèl·lules de Sertoli) i cèl·lules proliferants (limfòcits). En aplicar FISH en cèl·lules en proliferació s'estima que el 10,8% de dobles marques en excés trobades, en comparació amb les trobades en cèl·lules no proliferants, no són senyals partits, sinó deguts al procés de replicació. L'aplicació de FISH en cèl·lules en proliferació, com són els blastòmers, pot dificultar la interpretació dels resultats de FISH. Caldria incloure marcadors de l'inici o el final de la replicació per tal de ser usats simultàniament amb les sondes diagnòstiques de FISH en realitzar un DGP en blastòmers. El DGP per a la detecció d'aneuploïdies és un procediment més del que es disposa per tal d'oferir als pacients amb risc tot i que s'ha de valorar, en cada cas, si la seva aplicació pot ser beneficiosa.Cytogenetic analysis of the 1st polar body (1PB) allows an indirect characterisation of the oocyte in the metaphase II stage (MII) without compromising its reproductive capability. This allows, in an in vitro fertilisation treatment (IVF), the development of a variant of preimplantation genetic diagnosis in which the 1PB is analysed (PGD-1PB). The aim of this study is to analyse the aneuploidy rate in the female germ-cell line and in its first embryo development stages. We have used oocytes discarded from IVF cycles to develop a fluorescent in situ hybridisation (FISH) method that allows for the detection of nine chromosomes in 1PBs and in MII. Until now, missing chromosomes or chromatids in the 1PB have been considered as artefacts but the evaluation of the 1PB-MII complement could proves that they are only a minority (25.8%). Both the aneuploidy rate found for the nine chromosomes analysed (47.5%) and the estimated risk of aneuploidy for the 23 chromosomes (57.2%) are very high. The abnormal segregation percentage per analysed chromosome is 0.89%. Different mechanisms for the generation of aneuploidies have been identified: predivision of sister chromatids (more frequently observed in 1PB than in MII) and non-disjunction of homologous chromosomes in meiosis I and altered segregation in mitosis during the proliferative stage in the germ-cell line (gonadal mosaicism). This phenomenon has been found in 25.7% of the analysed patients and makes the application of prenatal diagnosis in patients which become pregnant after a PGD-1PB advisable. When applying PGD-1PB in females with a normal karyotype (advanced maternal age), the aneuploidy rate for the nine chromosomes is 60.4%, corroborating this group as a risk group for the presence of aneuploidies. Applying it to two female carriers of Robertsonian translocations, a high aneuploidy rate for the chromosomes not implicated in the translocation has been found (91.7% and 72.7%), independently of the alterations observed in the chromosomes of the translocation. The analysis of aneuploidies in blastomeres of male and female reciprocal translocation carriers shows a high aneuploidy rate for the chromosomes not involved in translocations (60.3%) and also a high percentage of mosaicism (58.7%), including both the chromosomes implicated and not implicated in the translocation. Normal and balanced embryos for the translocation, but with aneuploidies for other chromosomes, have been found. In translocation carriers, the sequential analysis of the segregation of the chromosomes involved in the translocation and the aneuploidy screening for other chromosomes seems necessary, In order to validate the interpretation of FISH results in the aneuploidy screening of proliferating cells, G0 stage cells (Sertoli cells) and proliferating cells (lymphocytes) have been studied. When applying FISH in proliferating cells, 10.8% extra double-dots found, in comparison with the ones found in non-proliferating cells, are not splits but are due to the replicating process. The use of FISH in proliferating cells as blastomeres could make the interpretation of FISH results difficult. It would be necessary to include markers of the beginning or the end of replication to be simultaneously used with other FISH probes in PGD-analysed blastomeres. PGD for aneuploidy screening is another procedure which is available to be offered to patients at risk although it has to be evaluated, case by case, to determine if its application can be beneficial

The human sperm basal body is a complex centrosome important for embryo preimplantation development

The mechanism of conversion of the human sperm basal body to a centrosome after fertilization, and its role in supporting human early embryogenesis, has not been directly addressed so far. Using proteomics and immunofluorescence studies, we show here that the human zygote inherits a basal body enriched with centrosomal proteins from the sperm, establishing the first functional centrosome of the new organism. Injection of human sperm tails containing the basal body into human oocytes followed by parthenogenetic activation, showed that the centrosome contributes to the robustness of the early cell divisions, increasing the probability of parthenotes reaching the compaction stage. In the absence of the sperm-derived centrosome, pericentriolar material (PCM) components stored in the oocyte can form de novo structures after genome activation, suggesting a tight PCM expression control in zygotes. Our results reveal that the sperm basal body is a complex organelle which converts to a centrosome after fertilization, ensuring the early steps of embryogenesis and successful compaction. However, more experiments are needed to elucidate the exact molecular mechanisms of centrosome inheritance in humans.F.A. was supported by a fellowship from the Agency for Management of University and Research Grants from the Government of Catalonia (AGAUR-2014 DI 065). Work in the Vernos lab was supported by the Spanish Ministry of Economy and Competitiveness (BFU2015-68726-P), the Ministry of Science, Innovation and Universities (PGC2018-096976-B-I00) and intramural funds from the Centre for Genomic Regulation. Intramural funding from Clínica EUGIN partially supported the study. We acknowledge the support of the Spanish Ministry of Economy, Industry and Competitiveness (MEIC) to the EMBL partnership, the Spanish Ministry of Economy and Competitiveness, Centro de Excelencia ‘Severo Ochoa’ and the CERCA programme/Generalitat de Cataluny

Novel Double Factor PGT strategy analyzing blastocyst stage embryos in a single NGS procedure

In families at risk from monogenic diseases affected offspring, it is fundamental the development of a suitable Double Factor Preimplantation Genetic Testing (DF-PGT) method for both single-gene analysis and chromosome complement screening. Aneuploidy is not only a major issue in advanced-maternal-age patients and balanced translocation carriers, but also the aneuploidy rate is extremely high in patients undergoing in vitro fertilization (IVF), even in young donors. To adequate NGS technology to the DF-PGT strategy four different whole genome amplification systems (Sureplex, MALBAC, and two multiple displacement amplification systems-MDA) were tested using TruSight One panel on cell lines and blastocyst trophectoderm biopsies-TE. Embryo cytogenetic status was analyzed by Nexus software. Sureplex and MALBAC DNA products were considered not suitable for PGT diagnosis due to inconsistent and poor results on Trusight one (TSO) panel. Results obtained with both MDA based methods (GEH-MDA and RG-MDA) were appropriate for direct mutation detection by TSO NGS platform. Nevertheless, RG-MDA amplification products showed better coverage and lower ADO rates than GEH-MDA. The present work also demonstrates that the same TSO sequencing data is suitable not only for the direct mutation detection, but also for the indirect mutation detection by linkage analysis of informative SNPs. The present work also demonstrates that Nexus software is competent for the detection of CNV by using with TSO sequencing data from RG-MDA products, allowing for the whole cytogenetic characterization of the embryos. In conclusion, successfully development of an innovative and promising DF-PGT strategy using TSO-NGS technology in TE biopsies, performed in-house in a single laboratory experience, has been done in the present work. Additional studies should be performed before it could be used as a diagnostic alternative in order to validate this approach for the detection of chromosomal aneuploidies

Rare predicted loss-of-function variants of type I IFN immunity genes are associated with life-threatening COVID-19

BackgroundWe previously reported that impaired type I IFN activity, due to inborn errors of TLR3- and TLR7-dependent type I interferon (IFN) immunity or to autoantibodies against type I IFN, account for 15-20% of cases of life-threatening COVID-19 in unvaccinated patients. Therefore, the determinants of life-threatening COVID-19 remain to be identified in similar to 80% of cases.MethodsWe report here a genome-wide rare variant burden association analysis in 3269 unvaccinated patients with life-threatening COVID-19, and 1373 unvaccinated SARS-CoV-2-infected individuals without pneumonia. Among the 928 patients tested for autoantibodies against type I IFN, a quarter (234) were positive and were excluded.ResultsNo gene reached genome-wide significance. Under a recessive model, the most significant gene with at-risk variants was TLR7, with an OR of 27.68 (95%CI 1.5-528.7, P=1.1x10(-4)) for biochemically loss-of-function (bLOF) variants. We replicated the enrichment in rare predicted LOF (pLOF) variants at 13 influenza susceptibility loci involved in TLR3-dependent type I IFN immunity (OR=3.70[95%CI 1.3-8.2], P=2.1x10(-4)). This enrichment was further strengthened by (1) adding the recently reported TYK2 and TLR7 COVID-19 loci, particularly under a recessive model (OR=19.65[95%CI 2.1-2635.4], P=3.4x10(-3)), and (2) considering as pLOF branchpoint variants with potentially strong impacts on splicing among the 15 loci (OR=4.40[9%CI 2.3-8.4], P=7.7x10(-8)). Finally, the patients with pLOF/bLOF variants at these 15 loci were significantly younger (mean age [SD]=43.3 [20.3] years) than the other patients (56.0 [17.3] years; P=1.68x10(-5)).ConclusionsRare variants of TLR3- and TLR7-dependent type I IFN immunity genes can underlie life-threatening COVID-19, particularly with recessive inheritance, in patients under 60 years old