Department of Genome Sciences, University of Washington, Seattle, WA 98105 and Department of Molecular & Medical Genetics, Oregon Health & Science University, Portland, OR 97239, USA.|Department of Genome Sciences, University of Washington, Seattle, WA 98105 and Department of Molecular & Medical Genetics, Oregon Health & Science University, Portland, OR 97239, USA.|Department of Genome Sciences, University of Washington, Seattle, WA 98105 and Department of Molecular & Medical Genetics, Oregon Health & Science University, Portland, OR 97239, USA.|Department of Genome Sciences, University of Washington, Seattle, WA 98105 and Department of Molecular & Medical Genetics, Oregon Health & Science University, Portland, OR 97239, USA.|Department of Genome Sciences, University of Washington, Seattle, WA 98105 and Department of Molecular & Medical Genetics, Oregon Health & Science University, Portland, OR 97239, USA.