Investigation of the RH locus in gorillas and chimpanzees

Abstract

The human Rh blood-group system is encoded by two homologous genes, RhD and RhCE. The RH genes in gorillas and chimpanzees were investigated to delineate the phylogeny of the human RH genes. Southern blot analysis with an exon 7-specific probe suggested that gorillas have more than two RH genes, as has recently been reported for chimpanzees. Exon 7 was well conserved between humans, gorillas, and chimpanzees, although the exon 7 nucleotide sequences from gorillas were more similar to the human D gene, whereas the nucleotide sequences of this exon in chimpanzees were more similar to the human CE gene. The intron between exon 4 and exon 5 is polymorphic and can be used to distinguish the human D gene from the CE gene. Nucleotide sequencing revealed that the basis for the intron polymorphism is an Alu element in CE which is not present in the D gene. Examination of gorilla and chimpanzee genomic DNA for this intron polymorphism demonstrated that the D intron was present in all the chimpanzees and in all but one gorilla. The CE intron was found in three of six gorillas, but in none of the seven chimpanzees. Sequence data suggested that the Alu element might have previously been present in the chimpanzee RH genes but was eliminated by excision or recombination. Conservation of the RhD gene was also apparent from the complete identity between the 3'-noncoding region of the human D cDNA and a gorilla genomic clone, including an Alu element which is present in both species. The data suggest that at least two RH genes were present in a common ancestor of humans, chimpanzees, and gorillas, and that additional RH gene duplication has taken place in gorillas and chimpanzees. The RhCE gene appears to have diverged more than RhD among primates. In addition, the RhD gene deletion associated with the Rh-negative phenotype in humans seems to have occurred after speciation.

The RHD gene is highly detectable in RhD-negative Japanese donors.

“…The nucleotide sequence of intron 4 in the RHD gene was entirely consistent with that reported by Huang. Comparing our data with the report of Westhoff et al (25), however, there are many nucleotide differences: two deletions (G at nucleotide 1, A at nucleotide 316), a single insertion (G next to nucleotide 426) in intron 4 of the RHD gene, four deletions (G at nucleotide 1, G at nucleotide 545, C at nucleotide 953, A at nucleotide 965), four insertions (G at nucleotide 308, A at nucleotide 409, G at nucleotide 414, G next to nucleotide 1075), and three substitutions (C→T at nucleotide 308, A→G at nucleotide 685, G→A at nucleotide 799) in intron 4 of the RHCE gene (Fig. 2).…”

“…Huang showed all sequences of intron 4 in the RHD gene, and indicated the existence of the human Alu repeat in intron 4 of the RHCE gene (24). Westhoff et al demonstrated the Alu element similar to Huang's report in addition to all sequences of intron 4 in both the RHD and RHCE genes (25). To identify intron 4 of the RHD gene and the RHCE genes, we carried out the PCR amplification with primers F3/R3.…”

Comparison of DNA and protein polymorphisms between humans and chimpanzees.

“…In red and green opsin genes, several polymorphic amino acids are shared by these paralogous loci in each of humans, chimpanzees and gorillas, suggesting frequent gene exchanges between the loci (Deeb et al 1994). Similarly, for the Rh locus, frequent gene exchanges between D and CE genes were reported (Westhoff and Wylie 1996). These sequence exchanges between loci either increase or decrease the extent of the neutral variation, depending on the size of the transferred segments (Ohta 1982).…”

“…Other polymorphism data Some other polymorphic loci have been examined at the nucleotide sequence level in humans and chimpanzees/gorillas: genes for pyruvate dehydrogenase E1 α subunit (PDHA1; Harris and Hey a: L = the number of loci examined, P = the number of polymorphic loci, H = the average heterozygosity b: n = the number of samples 1999), red and green opsins (Deeb et al 1994), Rh blood type (Rh; Westhoff and Wylie 1996), protamine 1 and 2 (Pr1 and Pr2) (Wyckoff et al 2000), and major histocompatibility complex (Mhc) ( e.g., de Groot et al 2000). At the PDHA1 locus the nucleotide diversity of 36 human and two chimpanzee DNA sequences were examined.…”

Gene arrangement at the Rhesus blood group locus of chimpanzees detected by fiber-FISH

“…Both RHCE and RHD have ten exons and the mRNA sequence identity between them was found to be about 96 % Le Van Kim et al, 1992;Cherif-Zahar et al, 1994). A distinct difference between these two genes lies in the length of intron 4; intron 4 of RHCE is about 650 bp longer than that of RHD due to Alu sequence insertion (Westhoff and Wylie, 1996;Huang 1997;Okuda et al, 1997). Recently, the DNA sequence homology between the two RH genes including all exons and introns was reported to be 91.7 % (Okuda et al, 2000).…”