LFNG

LFNG O-fucosylpeptide 3-beta-N-acetylglucosaminyltransferase, also known as LFNG and Lunatic Fringe, is a human is_associated_with::gene.

This gene encodes a member of the is_associated_with::glycosyltransferase superfamily. The encoded protein is a single-pass type II Golgi membrane protein that functions as a is_associated_with::fucose-specific glycosyltransferase, adding an is_associated_with::N-acetylglucosamine to the fucose residue of a group of signaling receptors involved in regulating cell fate decisions during development. Mutations in this gene have been associated with autosomal recessive spondylocostal dysostosis 3. Alternatively spliced transcript variants that encode different isoforms have been described, however, not all variants have been fully characterized.

Function
Lunatic Fringe (Lfng) is a gene whose role in embryonic development is to establish the anterior boundary of is_associated_with::somites, which will eventually develop in vertebrae, ribs, and dermis. Lunatic Fringe responds to certain threshold ratios of is_associated_with::retinoic acid and is_associated_with::FGF-8 in order to mark the anterior boundary of somites while another transcription factor, Hairy, responds to different threshold ratios of retinoic acid and FGF-8 to form the posterior boundaries of somites.

Clinical significance
A defect associated with Lfng mutations is is_associated_with::spondylocostal dysostosis. Spondylocostal dysostosis is characterized by segmentation problems in the developing vertebrae resulting in fusion or lack of vertebrae along with abnormalities in the ribs. Clinically, spondylocostal dysostosis presents as a shortened neck and trunk relative total height and a mild form of scoliosis. Respiratory problems are also common in spondylocostal dysostosis because of the shortened trunk.

A knockout model for Lfng has been created in mice, and without Lfng, mice have shorter tails, and impaired rib, lung, and somite development. A deficiency of Lfng in male mice has also been associated with lack of spermatozoa in the epididymis of many mice; however, spermatogenesis was not impaired. Rather, the male mice were subfertile. In female mice, Lfng deficiency led to infertility because of abnormal folliculogenesis. Further examination showed that oocytes from these female mice did not complete meiotic maturation. However, there are other studies that contradict this stating that not all female mile deficient of Lfng are infertile. A possible explanation for this difference between these studies is that the Lfng alleles were functional different, however, this is unlikely. More likely is that this discrepancy results from differences in the genetic background of the mice or husbandry and colony conditions.