Actin-like sequences are present on human X and Y chromosomes

Area of Science:

• Genetics
• Molecular Biology
• Human Genomics

Background:

• The human genome possesses over 20 actin-related sequences, with at least six expressed as proteins.
• Actin-like sequences have been previously detected on both X and Y chromosomes.

Purpose of the Study:

• To investigate the chromosomal localization and potential utility of actin-related sequences in the human genome.
• To determine if the Y-linked actin sequence can serve as a marker for sex determination anomalies.

Main Methods:

• Blot hybridization using cDNA probes for human alpha skeletal actin and hamster cytoskeletal actin.
• Analysis of HindIII digests of genomic DNA.
• Hybridization to DNA from human-mouse hybrid cell lines for chromosomal assignment.
• Genomic DNA analysis of individuals with sex determination anomalies (XX males, XX hermaphrodites).

Main Results:

• Actin-like sequences were confirmed on both X and Y chromosomes, showing greater homology to cytoskeletal actin probes.
• A polymorphic autosomal DNA fragment related to actin was identified with a major allele frequency of 0.55.
• The X-linked actin sequence was localized to a centromeric region (Xp11-Xq11), outside the proposed X-Y homology region.
• The Y-linked actin sequence was present in all XY males but absent in XX males and XX hermaphrodites, indicating it is not translocated in these conditions.

Conclusions:

• The Y-linked actin sequence is a valuable marker for analyzing sex determination and gametogenesis anomalies in humans.
• The identified Y-chromosome region containing the actin sequence is not translocated onto the X chromosome or autosomes in XX males or XX hermaphrodites.