Deciphering heterogeneity in pig genome assembly Sscrofa9 by isochore and isochore-like region analyses.
BACKGROUND
The isochore, a large DNA sequence with relatively small GC variance, is one of the most important structures in eukaryotic genomes. Although the isochore has been widely studied in humans and other species, little is known about its distribution in pigs.


RESULTS
In this paper, we construct a map of long homogeneous genome regions (LHGRs), i.e., isochores and isochore-like regions, in pigs to provide an intuitive version of GC heterogeneity in each chromosome. The LHGR pattern study not only quantifies heterogeneities, but also reveals some primary characteristics of the chromatin organization, including the followings: (1) the majority of LHGRs belong to GC-poor families and are in long length; (2) a high gene density tends to occur with the appearance of GC-rich LHGRs; and (3) the density of LINE repeats decreases with an increase in the GC content of LHGRs. Furthermore, a portion of LHGRs with particular GC ranges (50%-51% and 54%-55%) tend to have abnormally high gene densities, suggesting that biased gene conversion (BGC), as well as time- and energy-saving principles, could be of importance to the formation of genome organization.


CONCLUSIONS
This study significantly improves our knowledge of chromatin organization in the pig genome. Correlations between the different biological features (e.g., gene density and repeat density) and GC content of LHGRs provide a unique glimpse of in silico gene and repeats prediction.
Zhang
Wenqian
W
Bioinformatics Center, College of Life Science, Northwest A&F University, Xianyang, Shaanxi, China.
Wu
Wenwu
W
Lin
Wenchao
W
Zhou
Pengfang
P
Dai
Li
L
Zhang
Yang
Y
Huang
Jingfei
J
Zhang
Deli
D
D000818:Animals; D002874:Chromosome Mapping; D016678:Genome; D013552:Swine / Q000235:genetics*