STAT3 and androgen insensitivity syndrome: The key regulator of chondrocyte differentiation and skeletal development SOX9 transcription factor was also included in the list of genes to be investigated; SOX9 genetic variants were associated with AIS severity [32], and upregulated expression of SOX9 was described in AIS spinal facets [44] as induced by ghrelin hormone through the ERK/STAT3 signaling pathway.