A microsatellite-based, physically anchored linkage map for the gray, short-tailed Opossum (Monodelphis domestica)

Abstract

The genome of the gray, short-tailed opossum, Monodelphis domestica, will be the first of any marsupial to be fully sequenced. The utility of this sequence will be greatly enhanced by construction and integration of detailed genetic and physical maps. Therefore, it is important to verify the unusual recombinational characteristics that were suggested by the 'first-generation' M. domestica linkage map; specifically, very low levels of recombination and severely reduced female recombination, both of which are contrary to patterns in other vertebrates. We constructed a new linkage map based on a different genetic cross, using a new and much larger set of map markers, and physically anchored and oriented the linkage groups onto chromosomes via fluorescence in-situ hybridization mapping. This map includes 150 loci in eight autosomal linkage groups corresponding to the eight autosome pairs, and spans 86-89% of the autosomal genome. The sex-averaged autosomal map covers 715 cM, with a full-length estimate of 866 cM; the shortest full-length linkage map reported for any vertebrate. The sex-specific maps confirmed severely reduced female recombination in all linkage groups, and an overall F/M map ratio = 0.54. These results greatly extend earlier findings, and provide an improved microsatellite-based linkage map for this species.

Scrambling Eggs: Meiotic Drive and the Evolution of Female Recombination Rates

“…This pattern has been noted in fish (Sakamoto et al 2000;, humans (Broman et al 1998;Clark et al 2010), dogs (Wong et al 2010), and mice Paigen et al 2008), although there are some exceptions [e.g., opossums (Samollow et al , 2007]. Utilizing data from a recent fine-scale analysis of sex-specific recombination rate in humans (Kong et al 2010), we display an example of this pattern in Figure 1B.…”

Genome of the marsupial Monodelphis domestica reveals innovation in non-coding sequences

“…Current linkage data 38 show that the average recombination rate for the autosomes (,0.2-0.3 cM Mb 21 ) is lower than in other sequenced amniotes (0.5-.3 cM Mb 21 ). Consistent with the proposed model, the mean autosomal G1C content (37.7%) is also lower than in other sequenced amniotes (40.9-41.8%) and, in particular, the mean autosomal density of CpGs (0.9%) is twofold lower than in other amniotes (1.7-2.2%).…”

“…Extensions to these findings, as well as additional topics, are reported in a series of companion papers [31][32][33][34][35][36][37][38][39][40][41] .…”

“…2). Approximately 97% of the assembled sequence has been anchored to eight large autosomes and one sex chromosome on the basis of genetic markers mapped by linkage analysis 38 or fluorescence in situ hybridization 43 (FISH; Supplementary Note 3). The draft genome sequence has high continuity, coverage and accuracy (Table 1; Supplementary Note 4 and Supplementary Tables 1-7).…”

Kangaroo gene mapping and sequencing: insights into mammalian genome evolution

“…A microsatellite map of the opossum genome was later produced that could be anchored to opossum chromosomes (Samollow et al 2007). The numbers of markers for the tammar map were greatly expanded by searching for microsatellites within conserved genes which could be mapped by FISH, and this strategy enabled the linkage maps to be anchored to physical chromosomes (Wang et al 2011a).…”