title: Examination of FGFRL1 as a candidate gene for diaphragmatic defects at chromosome 4p16.3 shows that Fgfrl1 null mice have reduced expression of Tpm3, sarcomere genes and Lrtm1 in the diaphragm.
abstract: Fgfrl1 (also known as Fgfr5; OMIM 605830) homozygous null mice have thin, amuscular diaphragms and die at birth because of diaphragm hypoplasia. FGFRL1 is located at 4p16.3, and this chromosome region can be deleted in patients with congenital diaphragmatic hernia (CDH). We examined FGFRL1 as a candidate gene for the diaphragmatic defects associated with 4p16.3 deletions and re-sequenced this gene in 54 patients with CDH. We confirmed six known coding single nucleotide polymorphisms (SNPs): c.209G > A (p.Pro20Pro), c.977G > A (p.Pro276Pro), c.1040T > C (p.Asp297Asp), c.1234C > A (p.Pro362Gln), c.1420G > T (p.Arg424Leu), and c.1540C > T (p.Pro464Leu), but we did not identify any gene mutations. We genotyped additional CDH patients for four of these six SNPs, including the three non-synonymous SNPs, to make a total of 200 chromosomes, and found that the allele frequency for the four SNPs, did not differ significantly between patients and normal controls (p > or = 0.05). We then used Affymetrix Genechip Mouse Gene 1.0 ST arrays and found eight genes with significantly reduced expression levels in the diaphragms of Fgfrl1 homozygous null mice when compared with wildtype mice-Tpm3, Fgfrl1 (p = 0.004), Myl2, Lrtm1, Myh4, Myl3, Myh7 and Hephl1. Lrtm1 is closely related to Slit3, a protein associated with herniation of the central tendon of the diaphragm in mice. The Slit proteins are known to regulate axon branching and cell migration, and inhibition of Slit3 reduces cell motility and decreases the expression of Rac and Cdc42, two genes that are essential for myoblast fusion. Further studies to determine if Lrtm1 has a similar function to Slit3 and if reduced Fgfrl1 expression can cause diaphragm hypoplasia through a mechanism involving decreased myoblast motility and/or myoblast fusion, seem indicated.
authors.affiliation: Division of Genetics, Department of Pediatrics, University of California, 533 Parnassus St, Room U585P, San Francisco, CA 94143-0748, USA.
authors.forename: Nelson
authors.initials: N
authors.lastname: LopezJimenez
authors.forename: Simon
authors.initials: S
authors.lastname: Gerber
authors.forename: Vlad
authors.initials: V
authors.lastname: Popovici
authors.forename: Sonia
authors.initials: S
authors.lastname: Mirza
authors.forename: Kirsten
authors.initials: K
authors.lastname: Copren
authors.forename: Linda
authors.initials: L
authors.lastname: Ta
authors.forename: Gary M
authors.initials: GM
authors.lastname: Shaw
authors.forename: Beat
authors.initials: B
authors.lastname: Trueb
authors.forename: Anne M
authors.initials: AM
authors.lastname: Slavotinek
mesh_terms: D000818:Animals; D002894:Chromosomes, Human, Pair 4; D003964:Diaphragm / Q000002:abnormalities* / Q000378:metabolism; D015536:Down-Regulation / Q000235:genetics; D004622:Embryo, Mammalian; D005787:Gene Frequency; D056726:Genetic Association Studies; D006548:Hernia, Diaphragmatic / Q000235:genetics / Q000473:pathology; D065630:Hernias, Diaphragmatic, Congenital; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D010532:Peritoneal Diseases / Q000151:congenital / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide; D051500:Receptor, Fibroblast Growth Factor, Type 5 / Q000032:analysis / Q000235:genetics*; D012518:Sarcomeres / Q000235:genetics* / Q000378:metabolism; D014335:Tropomyosin / Q000235:genetics* / Q000378:metabolism
chemical_list: C417531:FGFRL1 protein, human; D051500:Receptor, Fibroblast Growth Factor, Type 5; C411923:Tpm3 protein, mouse; D014335:Tropomyosin