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Chromosoma (2009) 118:527536
DOI 10.1007/s00412-009-0216-6
RESEARCH ARTICLE
Molecular cloning and characterizationof the germline-restricted chromosome sequence in the zebra finch
Yuichiro Itoh & Kathy Kampf & Mara Ins Pigozzi &
Arthur P. Arnold
Received: 9 January 2009 /Revised: 30 March 2009 /Accepted: 30 April 2009 /Published online: 19 May 2009 # The Author(s) 2009. This article is published with open access at Springerlink.com
Abstract The zebra finch (Taeniopygia guttata) germline-restricted chromosome (GRC) is the largest chromosome and has a unique system of transmission in germ cells. In the male, the GRC exists as a single heterochromatic chromo-some in the germline and is eliminated from nuclei in late spermatogenesis. In the female, the GRC is bivalent and euchromatic and experiences recombination. These characteristics suggest a female-specific or female-beneficial function of the GRC. To shed light on the function of GRC, we cloned a portion of the GRC using random amplified polymorphic DNApolymerase chain reaction and analyzed it using molecular genetic and cytogenetic methods. The GRC clone hybridized strongly to testis but not blood DNA in genomic Southern blots. In fluorescent in situ hybridization analysis on meiotic chromosomes from synaptonemal complex spreads, the probe showed hybridization across a large area of the GRC, suggesting that it contains repetitive sequences. We isolated a sequence homologous to the GRC from zebra finch chromosome 3 and a region of chicken chromosome 1 that is homologous to zebra finch chromosome 3; the phylogenetic analysis of these three sequences suggested that the GRC sequence and the zebra finch chromosome 3 sequence are
most closely related. Thus, the GRC sequences likely originated from autosomal DNA and have evolved after the galliformpasseriform split. The present study provides a foundation for further study of the intriguing GRC.
The number of chromosomes differs between somatic and germline cells in several organisms; Acricotopus (Staiber 1987), sciarid flies (Goday and Esteban 2001), and some hagfish species (Kohno et al. 1986; Kubota et al. 1993). The extra chromosomes in the germline, germline-restricted chromosomes (GRCs), are eliminated during early embryo-genesis and do not exist in somatic cells. Thus, unlike A chromosomes, which are regular elements following Mendelian laws, GRCs have unique characteristics. In Acricotopus lucidus, there are nine different types of GRC distinguished by G-banding, which exist as various combinations in...