Mutations in the FTSJ1 Gene Coding for a Novel S-Adenosylmethionine–Binding Protein Cause Nonsyndromic X-Linked Mental Retardation

Kristine Freude, Kirsten Hoffmann, Lars-Riff Jensen, Martin B. Delatycki, Vincent des Portes, Bettina Moser, Ben Hamel, Hans van Bokhoven, Claude Moraine, Jean-Pierre Fryns, Jamel Chelly, Jozef Gécz, Steffen Lenzner, Vera M. Kalscheuer, Hans-Hilger Ropers

Nonsyndromic X-linked mental retardation (NSXLMR) is a very heterogeneous condition, and most of the underlying gene defects are still unknown. Recently, we have shown that approximately 30% of these genes cluster on the proximal Xp, which prompted us to perform systematic mutation screening in brain-expressed genes from this region. Here, we report on a novel NSXLMR gene, FTSJ1, which harbors mutations in three unrelated families--one with a splicing defect, one with a nonsense mutation, and one with a deletion of one nucleotide. In two families, subsequent expression studies showed complete absence or significant reduction of mutant FTSJ1 transcripts. FTSJ1 protein is a homolog of Escherichia coli RNA methyltransferase FtsJ/RrmJ and may play a role in the regulation of translation. Further studies aim to elucidate the function of human FTSJ1 and its role during brain development.