title: Contactin 4, -5 and -6 differentially regulate neuritogenesis while they display identical PTPRG binding sites.
abstract: The neural cell-adhesion molecules contactin 4, contactin 5 and contactin 6 are involved in brain development, and disruptions in contactin genes may confer increased risk for autism spectrum disorders (ASD). We describe a co-culture of rat cortical neurons and HEK293 cells overexpressing and delivering the secreted forms of rat contactin 4-6. We quantified their effects on the length and branching of neurites. Contactin 4-6 effects were different depending on the contactin member and duration of co-culture. At 4 days in culture, contactin 4 and -6 increased the length of neurites, while contactin 5 increased the number of roots. Up to 8 days in culture, contactin 6 progressively increased the length of neurites while contactin 5 was more efficient on neurite branching. We studied the molecular sites of interaction between human contactin 4, -5 or -6 and the human Protein Tyrosine Phosphatase Receptor Gamma (PTPRG), a contactin partner, by modeling their 3D structures. As compared to contactin 4, we observed differences in the Ig2 and Ig3 domains of contactin 5 and -6 with the appearance of an omega loop that could adopt three distinct conformations. However, interactive residues between human contactin 4-6 and PTPRG were strictly conserved. We did not observe any differences in PTPRG binding on contactin 5 and -6 either. Our data suggest that the differential contactin effects on neurite outgrowth do not result from distinct interactions with PTPRG. A better understanding of the contactin cellular properties should help elucidate their roles in ASD.
authors.affiliation: Human Genetics and Cognitive Functions, Institut Pasteur , 75015 Paris , France ; CNRS URA 2182 'Genes, synapses and cognition', Institut Pasteur , 75015 Paris , France ; Université Paris Diderot, Sorbonne Paris Cité, Human Genetics and Cognitive Functions , 75013 Paris , France.
authors.forename: Oriane
authors.initials: O
authors.lastname: Mercati
authors.forename: Anne
authors.initials: A
authors.lastname: Danckaert
authors.forename: Gwénaëlle
authors.initials: G
authors.lastname: André-Leroux
authors.forename: Marco
authors.initials: M
authors.lastname: Bellinzoni
authors.forename: Laura
authors.initials: L
authors.lastname: Gouder
authors.forename: Kazutada
authors.initials: K
authors.lastname: Watanabe
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Shimoda
authors.forename: Régis
authors.initials: R
authors.lastname: Grailhe
authors.forename: Fabrice
authors.initials: F
authors.lastname: De Chaumont
authors.forename: Thomas
authors.initials: T
authors.lastname: Bourgeron
authors.forename: Isabelle
authors.initials: I
authors.lastname: Cloëz-Tayarani
keywords: 3D modeling; Co-culture between HEK cells and primary neurons; Contactin; Neurite outgrowth; Neurite quantification; Protein tyrosine phosphatase receptor gamma; Rat primary cortical neurons