Complex sentence: SRY expression has been associated with an increased development of TH-ir neurons (SRY is shown to be a regulator of the tyrosine hydroxylase gene expression) leading to a slightly higher number of dopaminergic neurons in males compared to females in the substantia Nigra.
Split into simpler sentences: SRY expression has been associated with an increased development of dopaminergic neurons (tyrosine hydroxylase immunoreactive neurons). This is due to SRY being a regulator of the tyrosine hydroxylase gene expression leading to a slightly higher number of dopaminergic neurons in males compared to females in the substantia Nigra.