Differences between human sperm and somatic cell DNA in CpG methylation within the HLA class I chromosomal region.
OBJECTIVE
We investigated the possible negative regulatory mechanisms that repress classical human leukocyte antigen (HLA) class I gene expression in human spermatozoa and searched for novel testis-specific coding sequences that might be present in MHC class I chromosomal region.


METHODS
We performed a comparative DNA methylation analysis of this genomic region in both purified human spermatozoa and mononuclear blood cells from the same donors, using methylation-sensitive restriction enzymes followed by classical or pulsed field gel electrophoresis and hybridization with HLA class I locus-specific probes.


RESULTS
Unmethylated CpG sites were detected in the 3' part of HpaII tiny fragments of the HLA-F and HLA-G genes in spermatozoal DNA. In contrast, no difference was observed in the methylation status of the HLA-B, HLA-C, and HLA-E genes between germ and somatic cells. CpG unmethylation events were also detected in several parts of this chromosomal region (outside the known loci) in spermatozoal DNA.


CONCLUSIONS
These results suggest that this genomic region undergoes changes in its DNA methylation pattern during the developmental process. We hypothesize that these dynamic changes have functional importance, including a possible transcriptional activity of nonclassical class I genes and/or as yet undescribed testis-specific coding sequences.
Guillaudeux
T
T
Institut National de la Santé et de la Recherche Médicale, Unité 100, Hôpital de Pontchaillou Rennes, France.
D'Almeida
M
M
Girr
M
M
Rodriguez
A M
AM
Pontarotti
P
P
Fauchet
R
R
Le Bouteiller
P
P
D001483:Base Sequence; D002874:Chromosome Mapping; D004247:DNA / Q000737:chemistry* / Q000235:genetics*; D015342:DNA Probes; D016521:Electrophoresis, Gel, Pulsed-Field; D005805:Genes, MHC Class I; D006680:HLA Antigens / Q000235:genetics; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000737:chemistry / Q000276:immunology; D008297:Male; D008745:Methylation; D009693:Nucleic Acid Hybridization; D013094:Spermatozoa / Q000737:chemistry* / Q000276:immunology*
D015342:DNA Probes; D006680:HLA Antigens; D004247:DNA