The chick Lrrn1 gene. (a) Map of the genomic interval containing Lrrn1 at approximately 18.2 Mb on chromosome 12 (horizontal black line). Vertical black lines represent 0.1 Mb intervals. Horizontal arrows represent the transcriptional orientation of genes identified within this interval and described in the Ensembl database (v.42). Lrrn1 is flanked by cereblon (CRBN) and a predicted gene (Ensembl: ENSGALG00000020777) related to human SET domain and mariner transposase fusion gene (SETMAR). Genomic organization of Lrrn1 predicted from the 2.9 kb cDNA clone identified is expanded below (scale bar = 1 kb). Predicted exons are shown as rectangles and the single intron as a black line. Sizes are shown as nucleotides (nt). The entire predicted coding region is contained on exon 2 (black shaded rectangle). Black arrowheads above exon 2 show the location of degenerate PCR primers (CDCVIHW, amino acids 375–381, 1,487–1,507 nt; and PEPEIYW, amino acids 453–459, 1,721–1,741 nt) used to amplify the Lrrn1 cDNA region used as a probe. (b) Schematic diagram of the Lrrn1 protein consisting of 12 extracellular LRRs (black isosceles trapezia) flanked by amino-terminal and carboxy-terminal flanking domains (blue rectangles), and single Ig domain (orange horseshoe, positions of conserved cysteine residues are indicated) and a membrane proximal FnIII domain (green rectangle). The plasma membrane lipid bilayer is represented by black horizontal lines. Locations of endocytic sorting motifs (pink triangle and blue circle) in the short cytoplasmic (cyto) tail are shown. (c) Predicted sequence of the chick (Gallus gallus) Lrrn1 protein (Lrrn1-Gg in red) aligned to its mouse (Mus musculus; Lrrn1-Mm; Ensembl: ENSMUSP00000037096) and human (Homo sapiens; Lrrn1-Hs; Ensembl: ENSP00000314901) orthologues (obtained from the Ensembl database) using the ClustalW method. Sequence positions are numbered on the left and marked at intervals of ten amino acids by black dots above. Identical residues amongst all three sequences are shown as red characters, similar residues are shown as black bold characters and boxed in yellow. Protein motifs are indicated using the same colour coding as in (b). Amino-terminal signal peptide and transmembrane domains are shown as dashed lines. Asparagine residues predicted to be potential sites of N-glycosylation are highlighted by an open circle.