Untitled

Parma

2021

Animals

After discovering the Robertsonian translocation rob(1;29) in Swedish red cattle and demonstrating its harmful effect on fertility, the cytogenetics applied to domestic animals have been widely expanded in many laboratories in order to find relationships between chromosome abnormalities and their phenotypic effects on animal production. Numerical abnormalities involving autosomes have been rarely reported, as they present abnormal animal phenotypes quickly eliminated by breeders. In contrast, numerical sex chromosome abnormalities and structural chromosome anomalies have been more frequently detected in domestic bovids because they are often not phenotypically visible to breeders. For this reason, these chromosome abnormalities, without a cytogenetic control, escape selection, with subsequent harmful effects on fertility, especially in female carriers. Chromosome abnormalities can also be easily spread through the offspring, especially when using artificial insemination. The advent of chromosome banding and FISH-mapping techniques with specific molecular markers (or chromosome-painting probes) has led to the development of powerful tools for cytogeneticists in their daily work. With these tools, they can identify the chromosomes involved in abnormalities, even when the banding pattern resolution is low (as has been the case in many published papers, especially in the past). Indeed, clinical cytogenetics remains an essential step in the genetic improvement of livestock.

Section: Robertsonian Translocations (Rob)mentioning

confidence: 99%

Chromosome Abnormalities and Fertility in Domestic Bovids: A Review

Parma

2021

Animals

“…The dynamic nature of repetitive elements is clearly a basilar reason for genomic plasticity (e.g., [14,102,142,143]) and it is in fact a way of having a low impact on the euchromatic genome [14,97]. Today, an increasing body of evidence strongly validates the involvement of satDNA in the modulation of genomic architectures of a large number of taxa, as in the case of bovids [21,104,144,145], rodents [17,111,143,146], suiformes [57] or genets [147]. This largely extends beyond mammalian evolution, as it can also be observed in insects (e.g., [54,148]), reptiles (e.g., [149]), plants [150] and many other lineages.…”

Section: Modulating Genome Architecture With Satdnasmentioning

confidence: 99%

“…These sequences are essentially centromeric satDNAs, whose detailed physical and organizational analysis contributed much to better comprehend the chromosomal mechanism behind the rob (1;29) translocation [20,145]. In 2000, Chaves and colleagues suggested that this chromosomal abnormality might not be a single event [144] and in 2003, using centromeric satDNA sequences, the same group proposed, for the first time, a two-step mechanism for this rearrangement [20]. This translocation mechanism involved, besides the centric fusion of the two acrocentric chromosomes, the loss and reorganization of specific satDNA families that were retained in the translocated chromosome [20].…”

Section: Remodeling Genome Architecture Through Robertsonian Translocmentioning

confidence: 99%

Decoding the Role of Satellite DNA in Genome Architecture and Plasticity—An Evolutionary and Clinical Affair

Louzada

Lopes

Ferreira

et al. 2020

Genes

Repetitive DNA is a major organizational component of eukaryotic genomes, being intrinsically related with their architecture and evolution. Tandemly repeated satellite DNAs (satDNAs) can be found clustered in specific heterochromatin-rich chromosomal regions, building vital structures like functional centromeres and also dispersed within euchromatin. Interestingly, despite their association to critical chromosomal structures, satDNAs are widely variable among species due to their high turnover rates. This dynamic behavior has been associated with genome plasticity and chromosome rearrangements, leading to the reshaping of genomes. Here we present the current knowledge regarding satDNAs in the light of new genomic technologies, and the challenges in the study of these sequences. Furthermore, we discuss how these sequences, together with other repeats, influence genome architecture, impacting its evolution and association with disease.

“…However, as αsatI-5 is present in thousands of copies in all autosomal chromosomes in cattle [30], it is possible that some alpha satellite I repeats are appropriately methylated, while other repeats are more hyper-methylated than the overall proportion of methylation measured here in individual samples suggests. Alternatively, somatic tissue cellular composition may be subtly different in SCNT compared to AI derived fetuses and post-natal animals.…”

Section: Discussionmentioning

confidence: 80%

DNA Methylation at a Bovine Alpha Satellite I Repeat CpG Site during Development following Fertilization and Somatic Cell Nuclear Transfer

Couldrey

Wells

2013

PLoS ONE

Incomplete epigenetic reprogramming is postulated to contribute to the low developmental success following somatic cell nuclear transfer (SCNT). Here, we describe the epigenetic reprogramming of DNA methylation at an alpha satellite I CpG site (αsatI-5) during development of cattle generated either by artificial insemination (AI) or in vitro fertilization (IVF) and SCNT. Quantitative methylation analysis identified that SCNT donor cells were highly methylated at αsatI-5 and resulting SCNT blastocysts showed significantly more methylation than IVF blastocysts. At implantation, no difference in methylation was observed between SCNT and AI in trophoblast tissue at αsatI-5, however, SCNT embryos were significantly hyper-methylated compared to AI controls at this time point. Following implantation, DNA methylation at αsatI-5 decreased in AI but not SCNT placental tissues. In contrast to placenta, the proportion of methylation at αsatI-5 remained high in adrenal, kidney and muscle tissues during development. Differences in the average proportion of methylation were smaller in somatic tissues than placental tissues but, on average, SCNT somatic tissues were hyper-methylated at αsatI-5. Although sperm from all bulls was less methylated than somatic tissues at αsatI-5, on average this site remained hyper-methylated in sperm from cloned bulls compared with control bulls. This developmental time course confirms that epigenetic reprogramming does occur, at least to some extent, following SCNT. However, the elevated methylation levels observed in SCNT blastocysts and cellular derivatives implies that there is either insufficient time or abundance of appropriate reprogramming factors in oocytes to ensure complete reprogramming. Incomplete reprogramming at this CpG site may be a contributing factor to low SCNT success rates, but more likely represents the tip of the iceberg in terms of incompletely reprogramming. Until protocols ensure the epigenetic signature of a differentiated somatic cell is reset to a state resembling totipotency, the efficiency of SCNT is likely to remain low.