title: Adaptive Evolution Favoring KLK4 Downregulation in East Asians.
abstract: The human kallikrein (KLK) cluster, located at chromosome 19q13.3-13.4, encodes 15 serine proteases, including neighboring genes (KLK3, KLK2, KLK4, and KLK5) with key roles in the cascades of semen liquefaction, tooth enamel maturation, and skin desquamation. KLK2 and KLK3 were previously identified as targets of adaptive evolution in primates through different mechanisms linked to reproductive biology and, in humans, genome-wide scans of positive selection captured, a yet unexplored, evidence for KLK neutrality departure in East Asians. We perform a detailed evaluation of KLK3-KLK5 variability in the 1000 Genomes samples from East Asia, Europe, and Africa, which was sustained by our own sequencing. In East Asians, we singled out a 70-kb region surrounding KLK4 that combined unusual low levels of diversity, high frequency variants with significant levels of population differentiation (FST > 0.5) and fairly homogenous haplotypes given the large local recombination rates. Among these variants, rs1654556_G, rs198968_T, and rs17800874_A stand out for their location on putative regulatory regions and predicted functional effects, namely the introduction of several microRNA binding sites and a repressor motif. Our functional assays carried out in different cellular models showed that rs198968_T and rs17800874_A operate synergistically to reduce KLK4 expression and could be further assisted by rs1654556_G. Considering the previous findings that KLK4 inactivation causes enamel malformations in humans and mice, and that this gene is coexpressed in epidermal layers along with several substrates involved in either cell adhesion or keratinocyte differentiation, we propose KLK4 as another target of selection in East Asians correlated to tooth and epidermal morphological traits.
authors.affiliation: Instituto de Investigação e Inovação em Saúde, Universidade do Porto (I3S), Porto, Portugal Institute of Molecular Pathology and Immunology of the University of Porto (IPATIMUP), Porto, Portugal Department of Biochemistry and Molecular Biology-IUOPA, University of Oviedo, Oviedo, Spain Institute of Biomedical Sciences Abel Salazar (ICBAS), University of Porto, Porto, Portugal.
authors.forename: Patrícia Isabel
authors.initials: PI
authors.lastname: Marques
authors.affiliation: Instituto de Investigação e Inovação em Saúde, Universidade do Porto (I3S), Porto, Portugal Institute of Molecular Pathology and Immunology of the University of Porto (IPATIMUP), Porto, Portugal.
authors.forename: Filipa
authors.initials: F
authors.lastname: Fonseca
authors.affiliation: Instituto de Investigação e Inovação em Saúde, Universidade do Porto (I3S), Porto, Portugal Institute of Molecular Pathology and Immunology of the University of Porto (IPATIMUP), Porto, Portugal.
authors.forename: Tânia
authors.initials: T
authors.lastname: Sousa
authors.affiliation: Instituto de Investigação e Inovação em Saúde, Universidade do Porto (I3S), Porto, Portugal Institute of Molecular Pathology and Immunology of the University of Porto (IPATIMUP), Porto, Portugal.
authors.forename: Paulo
authors.initials: P
authors.lastname: Santos
authors.affiliation: Instituto de Investigação e Inovação em Saúde, Universidade do Porto (I3S), Porto, Portugal Institute of Molecular Pathology and Immunology of the University of Porto (IPATIMUP), Porto, Portugal.
authors.forename: Vânia
authors.initials: V
authors.lastname: Camilo
authors.affiliation: Department of Computational and Systems Biology, University of Pittsburgh.
authors.forename: Zélia
authors.initials: Z
authors.lastname: Ferreira
authors.affiliation: Department of Biochemistry and Molecular Biology-IUOPA, University of Oviedo, Oviedo, Spain.
authors.forename: Victor
authors.initials: V
authors.lastname: Quesada
authors.affiliation: Instituto de Investigação e Inovação em Saúde, Universidade do Porto (I3S), Porto, Portugal Institute of Molecular Pathology and Immunology of the University of Porto (IPATIMUP), Porto, Portugal sseixas@ipatimup.pt.
authors.forename: Susana
authors.initials: S
authors.lastname: Seixas
mesh_terms: D044466:Asian People / Q000235:genetics*; D015536:Down-Regulation / Q000235:genetics*; D019143:Evolution, Molecular; D005202:Asia, Eastern; D014644:Genetic Variation / Q000235:genetics*; D006801:Humans; D007610:Kallikreins / Q000235:genetics*; D012641:Selection, Genetic / Q000235:genetics
chemical_list: D007610:Kallikreins; C120801:kallikrein 4
keywords: cis-regulation; human adaptation; kallikreins; morphological traits; sequence variation; serine proteases