Novel retrotransposed imprinted locus identified at human 6p25

Area of Science:

• Epigenetics
• Genomics
• Evolutionary Biology

Background:

• Differentially methylated regions (DMRs) are key epigenetic markers associated with imprinted genes.
• Identifying novel imprinted loci is crucial for understanding gene regulation and disease mechanisms.

Purpose of the Study:

• To identify novel human imprinted loci using DMRs.
• To characterize the epigenetic regulation, evolution, and function of the newly identified FAM50B locus.

Main Methods:

• Quantitative DNA methylation analysis to detect DMRs.
• RNA sequencing to identify and analyze transcripts (sense and antisense).
• Comparative phylogenetic analysis of FAM50B orthologs across species.

Main Results:

• A unique DMR was identified at the 5'-end of FAM50B (6p25.2), indicating a candidate imprinted locus.
• FAM50B exhibits paternal allele-specific expression in most human tissues, with biallelic expression in the ovary.
• An antisense transcript, FAM50B-AS, is monoallelically expressed from the paternal allele.
• FAM50B originated in Therians via retrotransposition and acquired imprinting during Eutherian evolution.
• FAM50B expression is deregulated in testicular germ cell tumors, with frequent loss of imprinting in seminomas.

Conclusions:

• FAM50B is a newly identified imprinted gene with a complex evolutionary history.
• Imprinting of FAM50B is likely acquired during Eutherian evolution.
• Dysregulation and loss of imprinting of FAM50B in testicular tumors suggest its role in spermatogenesis and cancer.
• Parental origin of genes, like FAM50B, is critical for understanding diseases associated with the 6p25.2 region.