First findingof Gy(a-) phenotype in the Czech Republic since its discovery in 1967. Possible relationship to original probandsfound in the USA in 1967–1968

Overview

Introduction:
Dombrock blood group system consists of 2 antithetical antigens – Doa (DO 001) a Dob (DO 002), and3 high frequency antigens: Gya (DO 003), Hy (DO 004) a Joa (DO 005). DO glycoprotein is attached to the RBCmembrane by a GPI-anchor. It is a member of mono-ADP-ribosyltransferase family. DO gene is located on the shortarm of chromosome 12. It consists of three exons distributed over 14 kB of DNA. Ten alleles of DO gene have beenidentified. High frequency antigen Gya was discovered in 1967 by J. Swanson et al. Gy(a-) phenotype was found in1967 and 1968 in two families of Czechoslovak origin. Four molecular mechanisms have been found for this phenotype.The Gy(a-) phenotype is the null phenotype in the Dombrock system. Case report: We found a woman (V.F.)with an antibody against a high frequency antigen, which was identified as anti-Gya and V.F. cells as Gy(a-). We triedto explore possible relationship of V.F. to original probands from 1967 and 1968. We were provided with data of thetwo families for our search (personal communication). We also investigated V.F.’s brother, daughter and cousin. Methods:Serological investigations were performed using microcolumn system DiaMed ID. DNA analysis: DNA fromblood specimens was purified and PCR was performed. PCR products were sequenced. Genealogical searches wereperformed using ancient church records and official records on emigration to the USA in 19th century. Detailed searcheswere performed on V.F.’s family and on the first American family (SK). As for the second family, we performedgenealogical searches only on names existing in that time in V.F.’s home region. Results: Serology: V.F.: Do(a-b-); Hy-; Gy(a-). Anti-Gya. Antibody reacted 2+ in IAT, ± to 2+ in bromelain test. Brother: Do(a-b+); Hy+; Gy(a+), but weakerthan usual (probably heterozygous status Gya). Daughter: The same blood group ABO as in V.F., reaction of herRBC with V.F.’s serum positive 2+ in IAT, negative in bromelain test. Genomic DNA analysis: V.F.: Revealed a homojednotlizygoussingle nucleotide mutation IVS1-2a>g in the acceptor splice site of intron 1. This mutation is known to resultoutsplicing of exon 2. Sequencing specified DOB allele (378 T; 624 C; 793 G). Other three known mutations wereruled out. Cousin: No mutation in DO gene was found. Genealogical searches: No direct common ancestors of V.F.and American families were found, but ancestors of both V.F. and SK’s family lived in the beginning of the 19th centuryin the same village. Two names or names of their spouses from the second family were found in the same village,but we cannot confirm their identity. Conclusions: The mutation in DO gene in V.F. is the same as in three Gy(a-)persons discovered in 1967 and 1968. In V.F.’s and SK’s family’s ancestors’ home village consanguineous marriageswere probable, because the village has been existing since 14th century and about 2 or 3 hundred people used to livethere together for centuries. According to our findings we consider ancient consanguinity between V.F. and at leastSK’s family very likely.

Key words:
Dombrock, Gregory, phenotype Gy(a-), serology, DNA analysis, PCR, sequencing, genealogical searches