A cytogenetic and comparative map of camelid chromosome 36 and the minute in alpacas

Abstract

Recent advances in camelid genomics have provided draft sequence assemblies and the first comparative and gene maps for the dromedary (CDR) and the alpaca (LPA). However, no map information is currently available for the smallest camelid autosome-chr36. The chromosome is also of clinical interest because of its involvement in the minute chromosome syndrome (MCS) in infertile alpacas. Here, we developed molecular markers for camelid chr36 by direct sequencing CDR36 and LPA minute and by bioinformatics analysis of alpaca unplaced sequence scaffolds. We constructed a cytogenetic map for chr36 in the alpaca, llama, and dromedary and showed its homology to human chromosome 7 (HSA7) at 49.8-55.5 Mb. The chr36 map comprised seven markers, including two genes-ZPBP and WVC2. Comparative status of HSA7 was further refined by cytogenetic mapping of 16 HSA7 orthologs in camelid chromosomes 7 and 18 and by the analysis of HSA7-conserved synteny blocks across 11 vertebrate species. Finally, mapping chr36 markers in infertile alpacas confirmed that the minute chromosome was a derivative of chr36, but the small size was not a result of a large deletion or a translocation. Instead, cytogenetic mapping of 5.8S, 18S, and 28S rRNA genes (nucleolus organizer region (NOR)) revealed that the size difference between chr36 homologs in infertile alpacas was due to a heterozygous presence of NOR, whereas chr36 in fertile alpacas had no NOR. We theorized that the heterozygous NOR might affect chr36 pairing, recombination, and segregation in meiosis and, thus fertility.

Chromosomal Localization of Candidate Genes for Fiber Growth and Color in Alpaca (Vicugna pacos)

“…Alpaca chromosome slides were prepared from peripheral blood lymphocytes of normal alpacas according to standard protocols (Raudsepp and Chowdhary, 2008). We used Concanavalin A (Con A from Canavalia ensiformis , 20 μg/ml; Sigma Aldrich) as the mitogen, instead of Pokeweed, because Con A stimulates better proliferation of alpaca blood lymphocytes (Avila et al, 2015).…”

“…The first camelid chromosome map was based on Zoo-FISH revealing evolutionarily conserved synteny segments across the dromedary, human, cattle and pig (Balmus et al, 2007). This information was instrumental for starting systematic gene mapping in these species and the first cytogenetics maps for the alpaca genome were developed only recently (Avila et al, 2014a,b, 2015). Because of difficulties to unambiguously identify camelid chromosomes (Di Berardino et al, 2006; Avila et al, 2014b), the 230 cytogenetically mapped markers in alpaca (Avila et al, 2014a) will serve as critical references for FISH-mapping new genes and markers.…”

High‐quality whole‐genome sequence of an abundant Holarctic odontocete, the harbour porpoise (Phocoena phocoena)

“…We expect that some of these fragmented matches are the result of chromosomal rearrangements between domestic cattle and the harbour porpoise, two species that diverged approximately 60 Myrs ago within the Cetartiodactyla (Gatesy et al., ); we also expect that some other gaps are missing pieces in our assembly. Previous examinations of chromosomal rearrangements at this level (Avila et al., ; Kulemzina et al., , ; Pauciullo et al., ) have shown similar levels of synteny (i.e., some entirely matching chromosomes, others matching two to three pieces in the other taxa) between camel, pig and domestic cattle (Balmus et al., ). Based on these comparisons, we infer that our assembly represents a nearly complete genome of P. phocoena and that our largest scaffolds are nearly complete chromosomes.…”

An Autosomal Translocation 73,XY,t(12;20)(q11;q11) in an Infertile Male Llama (Lama glama) With Teratozoospermia

“…So far, only two structural abnormalities have been described in camelids. One is the Minute Chromosome Syndrome , which has been found in infertile female alpacas and llamas (Drew et al, 1999; Tibary, 2008; Avila et al, 2014b; Fellows et al, 2014) and involves the smallest autosome, chromosome 36 (Avila et al, 2015). The second is an autosomal translocation in an infertile male llama that has been briefly and incompletely described in a study, whose main goal was the development of molecular cytogenetics tools for camelids (Avila et al, 2014b).…”