ACAN Repeat Number Polymorphism in Patients with Idiopathic Short Stature

Idiopathic short stature (ISS) refers to non-syndromic growth failure without chronic disorders. The molecular basis of ISS remains largely unknown. Although a variable number of tandem repeats (VNTR) of 57 nucleotides in ACAN is known to correlate with the height of people in the general population, the role of this genetic variant in the etiology of ISS has not been studied.

We studied 128 Japanese patients with ISS, including 63 patients with prenatal and postnatal growth failure (small-for-gestational age-SS [SGA-SS]), and 100 control individuals. To examine the repeat numbers of ACAN VNTR, we amplified the VNTR-containing genomic region and analyzed the PCR products by gel electrophoresis. The accuracy of the results was confirmed by long-read next-generation sequencing.

The repeat numbers of the patient group were similarly distributed to those of the control group, and no patient had a very small number. Moreover, the repeat numbers of the shorter and longer alleles in each individual, as well as the average number of the two alleles, were comparable between the two groups. The height standard deviation scores obtained from 106 patients did not correlate with the repeat numbers. There was no difference in the repeat numbers between the SGA-SS or non-SGA ISS groups, and the control group.

The results of this study indicate that reduced repeat numbers of ACAN VNTR do not represent a monogenic cause or a major contributing factor for ISS. Our findings await further validation.