Kidney Week

Abstract: FR-OR034

Molecular Organization of the Kidney Connecting Tubules Separates Calcium and Water Transport

Session Information

• Electrolyte and Acid-Base Homeostasis: New Insights
  October 23, 2026 | Location: Room 405, Convention Center
  Abstract Time: 05:30 PM - 05:40 PM

Category: Fluid, Electrolytes, and Acid-Base Disorders

• 1101 Fluid, Electrolyte, and Acid-Base Disorders: Basic

Authors

• Bahena-López, Jessica Paola, Oregon Health & Science University, Portland, Oregon, United States

Jessica Paola Bahena-López, MD, PhD

• Su, Mingzhen, Charite - Universitatsmedizin Berlin, Berlin, BE, Germany

Mingzhen Su, MD, MBBS

• Curry, Joshua N., Charite - Universitatsmedizin Berlin, Berlin, BE, Germany

Joshua N. Curry, MD, PhD

• Thaitongsuk, Poomipat, Oregon Health & Science University, Portland, Oregon, United States

Poomipat Thaitongsuk

• Bachmann, Sebastian, Charite - Universitatsmedizin Berlin, Berlin, BE, Germany

Sebastian Bachmann, PhD

• Yang, Chao-Ling, Oregon Health & Science University, Portland, Oregon, United States

Chao-Ling Yang, MD

• Nelson, Jonathan W., University of Southern California, Los Angeles, California, United States

Jonathan W. Nelson, PhD

• Ellison, David H., Oregon Health & Science University, Portland, Oregon, United States

David H. Ellison, MD, FASN

Background

The renal connecting tubule (CNT) is a key nephron segment located between the distal convoluted tubule (DCT) and collecting duct (CD) and contributes to calcium, sodium, potassium, & water handling. Prior studies have suggested that discrete CNT subsegments are present in rodents, distinguished by either water transport (aquaporin 2; Aqp2; (PMID:11053048) or aldosterone-sensitivity (Hsd11b2; PMID:34143184). As the CNT lacks specific markers, represents a small fraction of kidney cells, and is difficult to isolate due to its location, we combined enriched snRNA-seq with immunostaining (IF) to resolve CNT cell types and test the hypothesis that transport pathways are spatially organized to separate calcium from water transport.

Methods

Kidneys from male constitutive Calbindin-D28k-Cre; INTACT mice generated an enriched distal tubule snRNA-seq dataset. CNT organization was validated by mouse kidney and microdissected tubule IF.

Results

Unsupervised clustering identified all major distal tubule cell types, from DCT to CD, and revealed two transcriptionally distinct CNT populations and a transitional segment. CNT clusters were defined as Slc12a3-negative and Calb1-and Scnn1g positive (PMID: 31253652) & designated CNT1 and CNT2. CNT1 showed a calcium-transport-dominant profile, with high expression of Trpv5, Slc8a1, Calb1, S100g, Kl, Vdr, Pth1r, and Casr, with minimal expression of Aqp2 or Hsd11b2. CNT2 showed minimal calcium-transport gene expression, with absent Trpv5, and robust expression of Aqp2, and Hsd11b2, consistent with a shift toward sodium- and water-regulatory functions. A third subsegment displayed an intermediate or transitional state, with lower expression of calcium-related genes and the appearance of Aqp2 and Hsd11b2. IF validated this organization at the protein level, showing a spatial progression from TRPV5-high/AQP2-negative segments near the DCT to AQP2-high/TRPV5-low segments near the collecting duct.

Conclusion

These findings define the CNT as a molecularly organized transition zone in which calcium- and water-transporting programs are largely separated, likely to reabsorb calcium before urinary concentration takes place.

Acknowledgment

JBL was supported by Ben Lipps ASN postdoctoral felloweship

Funding

• NIDDK Support