{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"institution":[{"name":"bioRxiv"}],"indexed":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T16:55:58Z","timestamp":1785430558663,"version":"3.56.0"},"posted":{"date-parts":[[2026,2,25]]},"group-title":"Molecular Biology","reference-count":21,"publisher":"openRxiv","license":[{"start":{"date-parts":[[2026,2,25]],"date-time":"2026-02-25T00:00:00Z","timestamp":1771977600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/publicdomain\/zero\/1.0\/"}],"funder":[{"award":["R01DK131101"],"award-info":[{"award-number":["R01DK131101"]}],"id":[{"id":"https:\/\/ror.org\/01cwqze88","id-type":"ROR","asserted-by":"publisher"}]},{"award":["R01DK018381"],"award-info":[{"award-number":["R01DK018381"]}],"id":[{"id":"https:\/\/ror.org\/01cwqze88","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"accepted":{"date-parts":[[2026,2,25]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                <jats:p>\n                  Alport syndrome (AS) is a major cause of chronic kidney failure and affects millions of people worldwide. Pathogenic variants in COL4A3, COL4A4, and COL4A5, which encode the collagen IV\n                  <jats:sup>\n                    <jats:bold>\u03b1345<\/jats:bold>\n                  <\/jats:sup>\n                  scaffold, compromise glomerular basement membrane (GBM) structure and function. However, the molecular mechanisms linking the &gt;5,000 reported variants to disease pathology remain poorly understood. To address this gap, we previously examined a distinctive variant, an 8-amino acid \u201cZ-appendage\u201d, added to the NC1 domain of the \u03b13 chain. Knock-in mice carrying this variant developed GBM abnormalities and proteinuria, implicating the NC1 hexamer as a critical determinant of GBM function and suggesting that the hexamer surface contains bioactive sites that may mediate signaling and\/or organization of macromolecular complexes. Given that approximately 80% of AS cases are associated with COL4A5 variants, including many within the NC1 hexamer, we asked whether relocating the Z-appendage from the \u03b13 NC1 subunit to the \u03b15 subunit produces similar pathology. Strikingly,\n                  <jats:italic>Col4a5-Z<\/jats:italic>\n                  mice did not develop proteinuria and showed only minor changes in GBM morphology. In contrast, the variant induced marked thickening of Bowman\u2019s capsule, accompanied by increased deposition of the collagen IV\n                  <jats:sup>\n                    <jats:bold>\u03b1121<\/jats:bold>\n                  <\/jats:sup>\n                  scaffold, increased fibrillar collagen, and cellular deposits. Structural modeling predicts that the collagen IV\n                  <jats:sup>\n                    <jats:bold>\u03b1565\u2013\u03b1121<\/jats:bold>\n                  <\/jats:sup>\n                  scaffold bearing two Z-appendages adopts an aberrant secondary structure that may stiffen the scaffold and occlude binding sites. Together, these findings reveal a bioactive role for the collagen IV\n                  <jats:sup>\n                    <jats:bold>\u03b1565\u2013\u03b1121<\/jats:bold>\n                  <\/jats:sup>\n                  scaffold in the Bowman\u2019s capsule basement membrane, with potential implications for other \u03b1565\u2013\u03b1121containing tissues such as the aorta and bladder.\n                <\/jats:p>","DOI":"10.64898\/2026.02.23.707599","type":"posted-content","created":{"date-parts":[[2026,2,25]],"date-time":"2026-02-25T19:30:19Z","timestamp":1772047819000},"source":"Crossref","is-referenced-by-count":0,"title":["An Alport variant illuminates the bioactivity of the collagen IV\n                  <sup>\u03b1565-<\/sup>\n                  <sup>\u03b1121<\/sup>\n                  scaffold in Bowman\u2019s capsule"],"prefix":"10.64898","author":[{"given":"E","family":"Pokidysheva","sequence":"first","affiliation":[{"name":"Division of Nephrology and Hypertension, Department of Medicine"},{"name":"Center for Matrix Biology; Vanderbilt University Medical Center, Nashville, TN, 37232"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"R.","family":"Koirala","sequence":"additional","affiliation":[{"name":"Division of Nephrology and Hypertension, Department of Medicine"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"B.","family":"Clarke","sequence":"additional","affiliation":[{"name":"Division of Nephrology and Hypertension, Department of Medicine"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"E.","family":"Delpire","sequence":"additional","affiliation":[{"name":"Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"S.","family":"Boudko","sequence":"additional","affiliation":[{"name":"Division of Nephrology and Hypertension, Department of Medicine"},{"name":"Center for Matrix Biology; Vanderbilt University Medical Center, Nashville, TN, 37232"},{"name":"Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, TN, 37232"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"BG.","family":"Hudson","sequence":"additional","affiliation":[{"name":"Division of Nephrology and Hypertension, Department of Medicine"},{"name":"Center for Matrix Biology; Vanderbilt University Medical Center, Nashville, TN, 37232"},{"name":"Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, TN, 37232"},{"name":"Department of Biochemistry, Vanderbilt University, Nashville, TN 37232"},{"name":"Vanderbilt-Ingram Cancer Center, Vanderbilt University, Nashville, TN 37232"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"54368","reference":[{"key":"2026022713053098000_2026.02.23.707599v1.1","doi-asserted-by":"publisher","DOI":"10.1002\/jemt.20564"},{"key":"2026022713053098000_2026.02.23.707599v1.2","doi-asserted-by":"publisher","DOI":"10.1074\/jbc.R600025200"},{"key":"2026022713053098000_2026.02.23.707599v1.3","doi-asserted-by":"publisher","DOI":"10.1016\/j.matbio.2016.08.005"},{"key":"2026022713053098000_2026.02.23.707599v1.4","doi-asserted-by":"publisher","DOI":"10.1016\/j.kint.2017.12.018"},{"key":"2026022713053098000_2026.02.23.707599v1.5","doi-asserted-by":"publisher","DOI":"10.1007\/s004670050804"},{"key":"2026022713053098000_2026.02.23.707599v1.6","unstructured":"K. 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