|Number of repeats||Counts (alleles)||Percentage|
Overview of repeats
It has been described by Albrecht et al. (2004) that expansions of seven repeats (an increase from 15 to 22 alanines) in the exon 1 of HOXD13 gene resulted in synpolydactyly (SPD). They found that the expressed protein in cells which had small expansion (22 repeats) was localised in the nucleus. However, at 24 repeats, the protein was in the nucleus in only 50% of cases. At longer expansions (29-36 repeats), the protein was found in the cytoplasm in almost all cases. Therefore, they suggested that expansions of alanine above a threshold of 29 repeats resulted the expressed protein to aggregate and that prevents its entering to nucleus (Albrecht et al., 2004). In another study on Chinese cohort, an eight-repeat expansion was observed in all affected individuals, which was not present in any of 50 controls (Xin et al., 2012).