Genetic associations at 53 loci highlight cell types and biological pathways relevant for kidney function.

Reduced glomerular filtration rate defines chronic kidney disease and is associated with cardiovascular and all-cause mortality. We conducted a meta-analysis of genome-wide association studies for estimated glomerular filtration rate (eGFR), combining data across 133,413 individuals with replication in up to 42,166 individuals. We identify 24 new and confirm 29 previously identified loci. Of these 53 loci, 19 associate with eGFR among individuals with diabetes. Using bioinformatics, we show that identified genes at eGFR loci are enriched for expression in kidney tissues and in pathways relevant for kidney development and transmembrane transporter activity, kidney structure, and regulation of glucose metabolism. Chromatin state mapping and DNase I hypersensitivity analyses across adult tissues demonstrate preferential mapping of associated variants to regulatory regions in kidney but not extra-renal tissues. These findings suggest that genetic determinants of eGFR are mediated largely through direct effects within the kidney and highlight important cell types and biological pathways

Crystal structures of PCNA mutant proteins defective in gene silencing suggest a novel interaction site on the front face of the PCNA ring.

Proliferating cell nuclear antigen (PCNA), a homotrimeric protein, is the eukaryotic sliding clamp that functions as a processivity factor for polymerases during DNA replication. Chromatin association factor 1 (CAF-1) is a heterotrimeric histone chaperone protein that is required for coupling chromatin assembly with DNA replication in eukaryotes. CAF-1 association with replicating DNA, and the targeting of newly synthesized histones to sites of DNA replication and repair requires its interaction with PCNA. Genetic studies have identified three mutant forms of PCNA in yeast that cause defects in gene silencing and exhibit altered association of CAF-1 to chromatin in vivo, as well as inhibit binding to CAF-1 in vitro. Three of these mutant forms of PCNA, encoded by the pol30-6, pol30-8, and the pol30-79 alleles, direct the synthesis of PCNA proteins with the amino acid substitutions D41A/D42A, R61A/D63A, and L126A/I128A, respectively. Interestingly, these double alanine substitutions are located far away from each other within the PCNA protein. To understand the structural basis of the interaction between PCNA and CAF-1 and how disruption of this interaction leads to reduced gene silencing, we determined the X-ray crystal structures of each of these mutant PCNA proteins. All three of the substitutions caused disruptions of a surface cavity on the front face of the PCNA ring, which is formed in part by three loops comprised of residues 21-24, 41-44, and 118-134. We suggest that this cavity is a novel binding pocket required for the interaction between PCNA and CAF-1, and that this region in PCNA also represents a potential binding site for other PCNA-binding proteins

X-ray crystal structure of the D41A/D42A mutant PCNA protein.

<p>(A) Front and side views of the D41A/D42A mutant PCNA protein. All three subunits are colored light pink, and the locations of the substituted amino acid residues are shown in the sphere representation. (B) Close up of an overlay of the wild-type PCNA protein (light blue) and the D41A/D42A mutant PCNA protein (light pink) are shown in the ribbon representation (RMSD of 0.529 Å). The positions of the α carbons of residues 41 to 44 are indicated.</p

Backbone α-carbon displacement.

<p>Backbone α-carbon displacement.</p

Native gel electrophoresis of wild-type and mutant PCNA proteins.

<p>Solutions of the wild-type PCNA protein, the G178S mutant PCNA protein, the R61A/D63A mutant PCNA protein, the L126A/I128A mutant PCNA protein, and the D41A/D42A mutant PCNA protein (0.1–1.0 mg/ml) were run on a non-denaturing polyacrylamide gradient gel (4–20%) and stained with Coomassie blue. The positions of the PCNA monomer and PCNA trimer are indicated.</p

Data collection and refinement statistics.

<p>Data collection and refinement statistics.</p

X-ray crystal structure of the L126/I128A mutant PCNA protein.

<p>(A) Front and side views of the L126A/I128A mutant PCNA protein. All three subunits are colored pale green, and the locations of the substituted amino acid residues are shown in the sphere representation. (B) Close up of an overlay of the wild-type PCNA protein (light blue) and the L126A/I128A mutant PCNA protein (pale green) are shown in the ribbon representation (RMSD of 0.835 Å). The positions of the α carbons of residues 41 to 44 and of residues 124 to 128 are indicated. (C) Close up of the structure of the L126A/I128A mutant PCNA protein shown in the cartoon representation. The side chains of D42 and R44 are shown in the stick representation. A portion of a PEG molecule and a chloride ion are shown in the stick and sphere representation, respectively. The 2Fo-Fc map contoured at 1 σ is shown.</p

X-ray crystal structure of the R61A/D63A mutant PCNA protein.

<p>(A) Front and side views of the R61A/D63A mutant PCNA protein. All three subunits are colored wheat, and the locations of the substituted amino acid residues are shown in the sphere representation. (B) Close up of an overlay of the wild-type PCNA protein (light blue) and the R61A/D63A mutant PCNA protein (wheat) are shown in the ribbon representation (RMSD of 0.317 Å). The positions of the α carbons of residues 21 to 24 and of residues 61 to 63 are indicated. (C) Close up of the structure of the R61A/D63A mutant PCNA protein shown in the cartoon representation. The N-terminus, β strand A₁, α helix A₁, and loop B are colored pale yellow.</p

Location of the three double alanine substitutions in PCNA.

<p>(A) Front and side views of the wild-type PCNA trimer (PDB entry 2OD8.pdb). The three subunits of PCNA are colored light blue, pale green, and pale yellow. The bound PIP motif is shown in the stick representation and colored red. (B) Close-up view of one subunit of PCNA with the location of each substituted amino acid residue shown in the sphere representation. The D41A/D42A, R61A/D63A, and L126A/I128A substitutions are colored light pink, wheat, and pale cyan, respectively. (C) Close-up view of one subunit of PCNA with the location of the residues comprising the surface cavity shown in the sphere representation.</p

Tailoring the surgical corridor to the basilar apex in the pretemporal transcavernous approach: morphometric analyses of different neurovascular mobilization maneuvers

Background: The pretemporal transcavernous approach (PTA) provides optimal exposure and access to the basilar artery (BA); however, the PTA can be invasive when vital neurovascular structures are mobilized. The goal of this study was to evaluate mobilization strategies to tailor approaches to the BA. Methods: After an orbitozygomatic craniotomy, 10 sides of 5 cadaveric heads were used to assess the surgical access to the BA via the opticocarotid triangle (OCT), carotid-oculomotor triangle (COT), and oculomotor-tentorial triangle (OTT). Measurements were obtained, and morphometric analyses were performed for natural neurovascular positions and after each stepwise expansion maneuver. An imaginary line connecting the midpoints of the limbus sphenoidale and dorsum sellae was used as a reference to normalize the measurements of BA exposure and to facilitate the clinical applicability of this technique. Results: In the OCT, the exposed BA segment ranged from − 1 ± 3.9 to + 6 ± 2.0 mm in length in its natural position. In the COT, the accessible BA segment ranged from − 4 ± 2.3 to − 2 ± 3.0 mm in length in its natural position. Via the OTT, the accessible BA segment ranged from − 7 ± 2.6 to − 5 ± 2.8 mm in length in its natural position. In the OCT, COT, and OTT, a posterior clinoidectomy extended the exposure down to − 6 ± 2.7, − 8 ± 2.5, and − 9 ± 2.9 mm, respectively. Conclusions: This study quantitatively evaluated the need for the expansion maneuvers in the PTA to reach BA aneurysms according to the patient’s anatomical characteristics