1. RHCE*ce48C,662G: a novel RHCE allele with RHD*DAU0 in cis in a proband from Azores Islands Background Results Conclusions Study Design / Methods The proband and her parents were investigated. The C, E, c, e type was determined by standard hemagglutination techniques. RHCE and RHD genes (genomic DNA) were amplified with exon-specific primers and sequenced. RHD zygosity was performed with the Inno-train RBC-Ready Gene ZygoFast kit. Inês MOSER 1, Cédric VRIGNAUD 2, Michèle ROUSSEL 2, Pedro MENDONÇA 3, Cristina FRAGA 3, Florian PECQUET 2, Maria José RORIGUES 1 Thierry PEYRARD 2,4 1 Laboratório de Referência de Imunohematologia, Centro de Sangue e da Transplantação de Lisboa IPST-IP, Lisboa, Portugal 2 Institut National de la Transfusion Sanguine, Centre National de Référence pour les Groupes Sanguins, Paris, France 3 Hospital do Divino Espírito Santo de Ponta Delgada EPE, Ponta Delgada, São Miguel, Açores, Portugal 4 INSERM UMR_S1134, Paris, France Corresponding author:  tpeyrard@ints.fr As of today, 153 RHCE alleles have been reported (NCBI/dbRBC/BGMUT database), which underlines the complexity and diversity of this gene. A 28 year-old female patient, native from Azores, São Miguel Island (Portuguese territory), was found to show a weak expression of the e antigen. Further study was carried out in order to find the molecular basis of this altered e expression. Altogether, our data show that the proband inherited from her father the RHCE*ce48C,662G and RHD*DAU0 alleles, and the family study allowed to conclude that these alleles are within the same Rh haplotype. RHCE*ce662G, also known as RHCE*ceBE, was described by Doscher A et al., Transfusion 2009 and Hue-Roye K et al. Vox Sang 2010. Hue-Roye K et al. reported that RHCE*ce662G encodes the low-prevalence Be a (RH36) antigen. In our case, we characterized a novel RHCE allele molecularly close to RHCE*ceBE, with one additional change, c.48G>C (exon 1), frequently found in RHCE*ce alleles of people of African ancestry. We were so far unable to check the Be a type of the proband and her father (scarcity of anti-Be a ). The proband was said to be Caucasian. However, as both RHCE*ce48C and RHD*DAU0 are commonly encountered in Africans, we hypothesize that the proband's father could have African ancestors, this being quite possible for historical reasons in this area of the Atlantic Ocean, off the coast of North Africa. We speculate that RHCE*ce48C, 662G codes for partial c and e antigens (and probably RHCE*ceBE as well), due to the close proximity of the Pro221Arg substitution with the E/e polymorphism site (Pro226Ala), in the so-called "Rh protein vestibule" (Flegel WA Curr Opin Hematol 2006). Finally, there is a likely genetic linkage between RHCE*ce48C,662G and RHD*DAU0 (as previously reported for RHCE*ceMO). However, in order to confirm this hypothesis, more similar cases need to be found in other unrelated people. The proband was D+C-E+c+e+, with a weak e reactivity (Bio-Rad gel-test 1+; Immucor tube centrifugation test 2+). RHCE sequencing showed the c.48C>G (p.Trp16Cys) and c.662C>G (p.Pro221Arg) changes (heterozygous state), with a RHCE*ce/RHCE*cE genotype. The RHD study revealed a RHD*DAU0/RHD*D genotype. These results raised the question whether the c.48C>G and c.662C>G mutations were on the same RHCE allele (in cis). The proband's parents were investigated. The father (D+C-E-c+e+) revealed a RHD*DAU0/RHD*d genotype (D/d with RHD zygosity test) and RHCE sequencing showed the c.48C>G and c.662C>G changes (heterozygous state). The mother (D+C+E+c+e+) had a D/D genotype (RHD zygosity test) and no alteration in RHCE. Red Blood Cells Molecular Testing and Genetics: RH – Poster SP247, AABB 2015, Anaheim CA – Transfusion 2015;55(Suppl3):153A Locations of the C/c polymorphismLocation of the E/e polymorphism Predicted location of the p.Pro221Arg amino acid change in the RHCE protein (adapted from Flegel WA, Curr Opin Hematol 2006) p.Pro221Arg Red blood cell surface Intracellular domain Rh vestibule 48G>C662C>G RHCE*ce48C,662G