A new strategy for mannose-binding lectin gene haplotyping

The mannose-binding lectin 2 (MBL2) gene is polymorphic and codes for a protein with an important role in the innate immune response, whose variants have been associated with a great number of diseases. Point variations have been described in the 5' regulatory region at positions -550 (MBL2*H or *L) and -221 (*X or *Y), in the 5' untranslated sequence at position +4 (*P or *Q), and in the coding sequence of exon 1 at codons 52, 54, and 57 (MBL2*A or D, A or B, and A or C, respectively). These can be in cis or in trans configuration. The different haplotypes influence the immunological phenotype of the individual, which makes MBL2 haplotyping very important. Previously described MBL2-typing methods do not present adequate haplotype resolution or are too complex and costly. We have developed a new MBL2-typing strategy that is economical and renders rapid and reliable results without ambiguities. We typed 202 individuals of European, 32 of African, and 16 of Oriental descent. Only five to six reactions from 10 possible PCR-SSPs (sequence-specific polymerase chain reactions) were sufficient to genotype one individual unambiguously. The reactions were specific for amplification of the variants located upstream of the coding sequence. The results were associated to the results of hybridizations of the amplified products with eight sequence-specific oligonucleotide probes (SSOP). The strategy led to identification of eight alleles: MBL2*HYPA, HYPD, LYPA, LYPB, LYPD, LYQA, LYQC, and LXPA. Their frequencies in each of the groups were similar to those of other populations studied to date, with MBL2*LYPD (g.[-550G>C; -221C>G; 4T>C; 223C>T; 230A>G; 239A>G]) being novel. All samples were found to be in Hardy-Weinberg equilibrium.