Molecular genetic analysis of a para-Bombay phenotype pedigree using PacBio sequencing technology

The para-Bombay phenotype is a rare red blood group characterized by weak H expression. Its distribution and genetic polymorphisms vary significantly across populations. Accurate genotyping is crucial for understanding its molecular basis and genetic heterogeneity, which is essential for multidisciplinary research in transfusion medicine. Third-generation sequencing offers robust technical support for such research. This study employed Pacific Biosciences (PacBio) sequencing to investigate the molecular genetic mechanisms within a para-Bombay pedigree.

Serological methods were used to screen suspected para-Bombay individuals. Peripheral blood samples were collected from the proband and family members. ABO, FUT1, and FUT2 genotypes were analyzed using PacBio single-molecule real-time (SMRT) sequencing. Sequences were aligned against NCBI and ISBT databases to identify gene variants, followed by pedigree analysis.

Through serological and genetic analysis, the proband had an A para-Bombay phenotype (secretor) with FUT1 c.551_552delAG homozygous and FUT2 c.390 C>T homozygous. Pedigree analysis confirmed an autosomal recessive inheritance pattern. The father and younger brother both carried the genotype FUT2 c.390 C>T/c.[390 C>T;418 A>T], and exhibited a Le(a-b+) secretor phenotype. The compound haplotype (in cis) FUT2 [c.390 C>T;c.418 A>T] had been reported previously. The complete coding sequence was submitted to GenBank (Accession No. PV648693).

This study demonstrates the application of PacBio sequencing for identifying the para-Bombay phenotype, expanding the scope for resolving challenging blood types. PacBio technology enables precise elucidation of the genetic basis of this phenotype, providing a reliable methodology for pedigree analysis. This study supplements the GenBank database with the complete coding sequence of a compound FUT2 variant.