SOX10 and hydrops fetalis: Thus, distinct hair bulb melanocyte populations can be distinguished by the expression of the so-called ‘early’ pigment cell differentiation markers SOX10 and c-KIT in the melanogenically active bulb region of HF, together with the expression of the master pigment cell transcription factor MITF, and down-stream differentiation-associated melanosome markers gp100 and Melan-A.