Most DC-SIGNR transcripts at mucosal HIV transmission sites are alternatively spliced isoforms

Abstract

The repeat region of DC-SIGNR (CD209L) is polymorphic on the genomic level, and, in a separate study, we observed a correlation between the DC-SIGNR genotype and HIV-1 susceptibility during sexual contact. However, previous investigations using immunohistochemistry failed to detect membrane-bound DC-SIGNR on cells in the genital and rectal mucosa. We therefore explored the presence of DC-SIGNR in these compartments with a more sensitive limiting dilution RT-PCR, which also allowed for quantification of alternatively spliced mRNA isoforms. DC-SIGN (CD209) and DC-SIGNR mRNA transcript isoforms were found in all 12 vaginal and two rectal biopsies obtained from 14 healthy individuals. For DC-SIGNR, we detected significantly more isoform than full-length transcripts (mean copy numbers/lg RNA: 602 vs 26; P ¼ 0.0009). Four mucosal samples lacked full-length DC-SIGNR transcripts entirely. Cloning and sequencing of DC-SIGNR mRNA in three additional individuals revealed a diverse repertoire of DC-SIGNR isoforms, many of which encoded for proteins predicted to be soluble and secreted. Indeed, in one vaginal sample, we detected only soluble isoforms. In conjunction with our prior observation that the DC-SIGNR genotype has an effect on HIV-1 transmission in vivo, these findings emphasize that DC-SIGNR, in addition to DC-SIGN, should be considered as a cofactor in sexual HIV-1 transmission. Soluble isoforms, in particular, may modulate the efficiency of viral transmission and dissemination.

Structural Requirements for Multimerization of the Pathogen Receptor Dendritic Cell-specific ICAM3-grabbing Non-integrin (CD209) on the Cell Surface

“…1B). Therefore, and in agreement with previous reports (14,36,39), the DC-SIGN gene gives rise to a large number of alternatively spliced mRNA species, most of which differ in the number of 23-residue repeats within the neck domain, previously demonstrated to mediate multimerization of recombinant DC-SIGN (34).…”

“…express a high number of alternatively spliced DC-SIGN mRNA species (36), which are also found at mucosal HIV transmission sites (39). To determine the range of DC-SIGN mRNA species found in MDDC from a single donor, three different set of primers were designed to specifically amplify the prototypical DC-SIGN mRNA (DC-SIGN 1A), or species encoding either an alternative cytoplasmic domain (DC-SIGN 1B) or lacking the transmembrane domain (DC-SIGN ⌬TM) (Fig.…”

“…Five different alleles for the DC-SIGN neck domain have been identified to date, whose presence correlates with altered susceptibility to HIV-1 transmission (38). The functional relevance of the DC-SIGN neck variants has been further suggested by their detection at mucosal HIV transmission sites (39). Given the involvement of the neck domain in recombinant DC-SIGN multimerization, we hypothesized that the existence of this large array of polymorphic variants might have an impact on the repertoire of pathogen recognition by dendritic cells, as well as on the establishment of interactions between dendritic cells and other cell types.…”

Modern origin of numerous alternatively spliced human introns from tandem arrays

“…Polymorphisms in the tandem-repeat sequence of the thymidylate synthase gene are used as markers for effectiveness of 5-fluorouracil in cancer patients (42)(43)(44). Moreover, polymorphisms in the VNTR of the sirtuin and CD209 genes are associated with human longevity and HIV-1 transmission, respectively (29,37). These observations raise the intriguing possibility that individual-specific differences in such rapidly evolving and transcribed genomic regions have an impact on alternative splicing.…”

“…Last, at least 12 intron-breeding repeats identified in our study have been described as variable number of tandem repeats (VNTR) (minisatellites) and hence are highly polymorphic within the human population (28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40)(41)(42)(43)(44). Polymorphisms in the tandem-repeat sequence of the thymidylate synthase gene are used as markers for effectiveness of 5-fluorouracil in cancer patients (42)(43)(44).…”