PHF8(PHD finger protein 8) is a Fe²⁺ and 2-oxoglutarate dependent histone lysine demethylase and belongs to a family of JmjC domain-containing proteins. PHF8 also contains a plant homeodomain (PHD) finger motif in its N-terminus, which involves in transcriptional regulation. PHF8 can demethylate H3K9me2/1, H4K20me1 and H3K27me2 with JmjC domain, and also act as a transcriptional coactivator through binding to H3K4me3 via PHD finger. PHF8 regulates expression of rRNA and many protein-coding genes involved in neural development such as JARID1C. Mutations in human PHF8 which are defective in histone demethylase activity can cause inherited X-linked mental retardation(XLMR) and cleft lip/cleft palate. These researches suggested that PHF8 is an important regulator of neural development, which deepens the understanding of histone methylation with gene expression and provides novel clues to understanding of XLMR.