Chromosomes Of Maternal Origin Research Articles

The use of Karyomapping for genomic evaluation and PGT-A of preimplantation cattle embryos: the first live-born calves

Objectives Karyomapping was developed as a means of screening for monogenic and chromosomal disorders simultaneously in human IVF embryos using SNP chips. SNP chips in cattle breeding on the other hand are used for genomic selection i.e. to establish estimated breeding values (e.g. for food conversion efficiencies, milk production etc.). This has led to significantly improved rates of genetic gain through the screening and selection of animals at birth, but with the inherent drawback of having to wait for calf to be born before the result can be obtained and the fact that improvements within a herd breed are limited by the number of animals born. Application of genomic selection to in vitro produced (IVP) embryos however could bring further benefits thanks to the ability to test a greater number of individuals in a shorter time, thereby increasing selection speed and intensity. Aneuploidy is common in IVP embryos and could lead to developmental arrest. Karyomapping can therefore allow simultaneous genomic selection and aneuploidy detection, offering the power to maximise pregnancy rates of high quality offspring. Moreover, Karyomapping can be used to characterise the frequency and parental origin of aneuploidy. The objective of this study therefore was to apply Karyomapping to cattle breeding with a view to establishing the first live births by this approach. Method We used Karyomapping to characterise the frequency and parental origin of aneuploidy in IVP bovine embryos in order to establish an estimate of total aneuploidy rates in each parental germline. Furthermore, estimations of genome wide recombination rates in cattle were obtained and we performed the first embryo transfers. Results Following Karyomapping of trophectoderm biopsies, 68.8% of the embryos (n=42/61) appeared euploid while the rest displayed one or more abnormalities. Trisomies were detected with a frequency of 2.10% (n=68/3248 chromosomes) while monosomies with a frequency of just 0.31% (n=10/3248 chromosomes) resulting in a statistically significant difference. Monosomies appeared with a similar frequency of 0.24% (n=4/1653) and 0.36% (n=6/1653) in chromosomes of paternal and maternal origin, respectively. However, trisomies appeared with a frequency of 2.60% (n=43/1653) in chromosomes of maternal origin while the frequency for paternal chromosomes was 1.51% (n=25/1653) resulting in a significant difference. The average genome-wide recombination distance per Mb was calculated as 1.67 cM/Mb, which is higher than previous studies. Moreover, the maternal X chromosome showed a much-reduced number of crossovers than other chromosomes of similar size. Following transfer of euploid embryos, 4 live births are reported at time of writing. Conclusions We demonstrate, for the first time, a proof of principle for the application of Karyomapping to cattle breeding, with the birth of four calves after analysis in this way. This combined genomic selection and PGT-A approach was highly reliable, with calves showing 98% concordance with their respective embryo biopsies for SNP typing and 100% concordance with their respective biopsies for aneuploidy screening. This approach permits a significant increase in the rate of genetic gain and is applicable to basic research to investigate meiosis and aneuploidy in cattle.

Epigenetic status of imprinted genes in placenta during recurrent pregnancy loss

An analysis of differential methylation of 47 imprinted genes in placenta tissues of spontaneous abortions at the first trimester of pregnancy from women with recurrent pregnancy loss or with one sporadic abortion was performed using the DNA-microarray approach. We showed that epimutations of the imprinted genes were registered significantly more often in abortions from women with recurrent miscarriage in contrast to the embryos from women with sporadic pregnancy loss with frequency of 6.2 and 3.7% per locus, respectively (p < 0.01). The predominant type of epimutation appeared to be a postzygotic hypomethylation of the imprinted genes on chromosomes of maternal origin, which was observed in the examined samples in 5.1 and 2.89% of cases, respectively. Replicative study of the methylation status of seven imprinted genes (DLK1, PEG10, PLAGL1, KCNQ1OT1, PEG3, GRB10, and PEG1/MEST) in the enlarged embryo samples supported the results of microarray analysis in respect to both epimutation frequency and predominance of somatic hypomethylation of maternal alleles. It was also demonstrated that pregnancy loss was associated with multilocus methylation defects of imprinted genes, the frequency of which was also significantly increased in the placental tissues of spontaneous abortions in women with recurrent miscarriage.

Critical role of Yp inversion in &lt;i&gt;PRKX/PRKY&lt;/i&gt;-mediated Xp;Yp translocation in a patient with 45,X testicular disorder of sex development

45,X testicular disorder of sex development (TDSD), previously known as 45,X maleness, with unbalanced Xp;Yp translocation is an extremely rare condition caused by concomitant occurrence of loss of an X chromosome of maternal origin and an aberrant Xp;Yp translocation during paternal meiosis. We identified a Japanese male infant with an apparently 45,X karyotype who exhibited chondrodysplasia punctata and growth failure. Cytogenetic analysis revealed a 45,X.ish der(X)t(X;Y)(p22.33;p11.2)(DXZ1+,SRY+) karyotype. Array comparative genome hybridization analysis showed a simple Xp terminal deletion involving SHOX and ARSE with the breakpoint just centromeric to PRKX, and an apparently complex Yp translocation with the middle Yp breakpoint just telomeric to PRKY and the centromeric and the telomeric Yp breakpoints around the long inverted repeats for the generation of a common paracentric Yp inversion. Subsequently, a long PCR product was obtained with an X-specific and a Y-specific primers that were designed on the assumption of the presence of a Yp inversion that permits the alignment of PRKX and PRKY in the same direction, and the translocation fusion point was determined to reside within a 246 bp X-Y homologous segment at the "hot spot A" in the 5' region of PRKX/PRKY, by sequential direct sequencing for the long PCR product. These results argue not only for the presence of rare 45,X-TDSD with Xp;Yp translocation, but also for a critical role of a common paracentric Yp inversion in the occurrence of PRKX/PRKY-mediated unbalanced Xp;Yp translocation.

An emerging phenotype of interstitial 15q25.2 microdeletions: Clinical report and review

Interstitial deletions of chromosome 15q25.2 are rare. To date, only nine patients with microdeletions within this chromosomal region have been described. Here, we report on a girl with severe speech and psychomotor delay, behavioral problems and mild dysmorphic features with a 1.6 Mb deletion in 15q25.2 region. In order to study the parental origin of the rearrangement, we analyzed selected SNPs in the deleted area in the patient and her parents, showing Mendelian incompatibilities suggesting a de novo deletion on the chromosome of maternal origin. By comparing the clinical and molecular features of our patient with five previously reported cases of an overlapping deletion, we suggest that 15q25.2 deletion is an emerging syndrome characterized by a distinct although variable spectrum of clinical manifestations, including mild dysmorphic features, neurodevelopmental delay, and a recognizable pattern of congenital malformation. Furthermore, our patient is the second one in which a behavioral phenotype characterized by hyperactivity, anxiety, and autistic features was reported, indicating that these features might be part of this new syndromic condition. Breakpoints of the deletion in the patient reported here are useful to better define the smallest region of overlap (SRO) among all the patients. Selected genes that are present in the hemizygous state and which might be important for the phenotype of these patients, are discussed in context of the clinical features. In conclusion, our patient increases the knowledge about the molecular and phenotypic consequences of interstitial 15q25.2 deletions, highlighting that deletions of this region may be responsible for a new microdeletion syndrome.

CTCF-Dependent Chromatin Insulator Is Linked to Epigenetic Remodeling

Chromatin insulators are boundary elements between distinctly regulated, neighboring chromosomal domains, and they function by blocking the effects of nearby enhancers in a position-dependent manner. Here, we show that the SNF2-like chromodomain helicase protein CHD8 interacts with the insulator binding protein CTCF. Chromatin immunoprecipitation analysis revealed that CHD8 was present at known CTCF target sites, such as the differentially methylated region (DMR) of H19, the locus control region of beta-globin, and the promoter region of BRCA1 and c-myc genes. RNA interference-mediated knockdown of CHD8 significantly abolished the H19 DMR insulator activity that depends highly on CTCF, leading to reactivation of imprinted IGF2 from chromosome of maternal origin. Further, the lack of CHD8 affected CpG methylation and histone acetylation around the CTCF binding sites, adjacent to heterochromatin, of BRCA1 and c-myc genes. These findings provide insight into the role of CTCF-CHD8 complex in insulation and epigenetic regulation at active insulator sites.

Neuroblastoma in Two Siblings Supports the Role of 1p36 Deletion in Tumor Development

Familial neuroblastoma occurs rarely. We studied a family with three children; one of them has a disseminated (stage 4) and another has a localized (stage 2) neuroblastoma. We observed subtelomeric locus D1Z2 (1p36) deletion in both tumors by using double-color fluorescence in situ hybridization. The MYNC gene was found in single copy in both tumors. Loss of heterozygosity (LOH) and restriction fragment length polymorphism analyses were performed by using DNA from frozen tumor cells and from microdissected tumor areas excised from paraffin-embedded sections. We detected somatic LOH at locus D1S468 (1p36) in a tumor-cell population with a trisomy 1 of the stage-2 patient. Neuroblastoma cells of the stage-4 patient were diploid and showed allelic loss at the following loci: D1S172, D1S80, D1S94, D1S243, D1S468, D1S214, D1S241, and D1S164. Haplotype study showed that the siblings inherited the same paternal 1p36→pter chromosome region by homologous recombination and that, in the two tumors, arm 1p of different chromosomes of maternal origin was damaged. Our results suggest that the siblings inherited the predisposition to neuroblastoma associated with paternal 1p36 region and that tumors developed as a consequence of somatic loss of the maternal 1p36 allele.