title: Cyclostomes Lack Clustered Protocadherins.
abstract: The brain, comprising billions of neurons and intricate neural networks, is arguably the most complex organ in vertebrates. The diversity of individual neurons is fundamental to the neuronal network complexity and the overall function of the vertebrate brain. In jawed vertebrates, clustered protocadherins provide the molecular basis for this neuronal diversity, through stochastic and combinatorial expression of their various isoforms in individual neurons. Based on analyses of transcriptomes from the Japanese lamprey brain and sea lamprey embryos, genome assemblies of the two lampreys, and brain expressed sequence tags of the inshore hagfish, we show that extant jawless vertebrates (cyclostomes) lack the clustered protocadherins. Our findings indicate that the clustered protocadherins originated from a nonclustered protocadherin in the jawed vertebrate ancestor, after the two rounds of whole-genome duplication. In the absence of clustered protocadherins, cyclostomes might have evolved novel molecules or mechanisms for generating neuronal diversity which remains to be discovered.
authors.affiliation: Institute of Molecular and Cell Biology, A*STAR, Biopolis, Singapore.
authors.forename: Vydianathan
authors.initials: V
authors.lastname: Ravi
authors.affiliation: Institute of Molecular and Cell Biology, A*STAR, Biopolis, Singapore Animal Gene Editing Laboratory, Biological Resource Centre, A*STAR, Singapore.
authors.forename: Wei-Ping
authors.initials: WP
authors.lastname: Yu
authors.affiliation: Institute of Molecular and Cell Biology, A*STAR, Biopolis, Singapore.
authors.forename: Nisha E
authors.initials: NE
authors.lastname: Pillai
authors.affiliation: Institute of Molecular and Cell Biology, A*STAR, Biopolis, Singapore.
authors.forename: Michelle M
authors.initials: MM
authors.lastname: Lian
authors.affiliation: Institute of Molecular and Cell Biology, A*STAR, Biopolis, Singapore.
authors.forename: Boon-Hui
authors.initials: BH
authors.lastname: Tay
authors.affiliation: Institute of Molecular and Cell Biology, A*STAR, Biopolis, Singapore.
authors.forename: Sumanty
authors.initials: S
authors.lastname: Tohari
authors.affiliation: Institute of Molecular and Cell Biology, A*STAR, Biopolis, Singapore Okinawa Institute of Science and Technology Graduate University, Onna-son, Okinawa, Japan.
authors.forename: Sydney
authors.initials: S
authors.lastname: Brenner
authors.affiliation: Institute of Molecular and Cell Biology, A*STAR, Biopolis, Singapore mcbbv@imcb.a-star.edu.sg.
authors.forename: Byrappa
authors.initials: B
authors.lastname: Venkatesh
mesh_terms: D000818:Animals; D015820:Cadherins / Q000737:chemistry / Q000235:genetics*; D023061:Gene Order; D016678:Genome; D006801:Humans; D007568:Jaw; D007798:Lampreys / Q000033:anatomy & histology* / Q000235:genetics*; D005810:Multigene Family; D014714:Vertebrates
chemical_list: D015820:Cadherins
keywords: jawless vertebrates; neuronal diversity; protocadherin