Key Points Dehydrated hereditary stomatocytosis is characterized by abnormal RBC morphology but may involve pseudohyperkalemia and perinatal edema. This syndrome is associated with germline mutations in PIEZO1, encoding a transmembrane protein that induces mechanosensitive currents.

Mutations in the human

The cellular and subcellular localizations of the AE2 anion exchanger in rat kidney have remained elusive despite detection of moderately abundant AE2 mRNA and AE2 polypeptide in all kidney regions. In this report a simple epitope unmasking technique has allowed the immunolocalization of AE2 antigenic sites in basolateral membranes of several rat kidney tubular epithelial cells. AE2 immunostaining was faint or absent in the glomerulus and proximal tubule, present in descending and ascending thin limbs, and stronger in the medullary thick ascending limb (MTAL). A lower staining intensity was found in cortical thick ascending limbs and even less in the distal convoluted tubule. In contrast, there was an enhanced staining in the macula densa. In principal cells (PC) of the connecting segment, AE2 was undetectable but gradually increased in intensity along the collecting duct, with strongest staining in inner medullary collecting duct (IMCD) PC. A sodium dodecyl sulfate-sensitive AE2-related Golgi epitope was also detected in some interstitial and endothelial cells of the inner medulla and in epithelial cells of IMCD and MTAL. Colchicine treatment of the intact animal altered the distribution of this Golgi-associated epitope but left plasmalemmal AE2 undisturbed. Reverse transcription-polymerase chain reaction detected AE2a, AE2b, and AE2c2 but not AE2c1 transcripts in rat kidney mRNA. The results suggest a widespread occurrence of the AE2 protein in several renal epithelial cell types.

We have characterized expression of anion exchanger 2 (AE2) mRNA and protein in the mouse intestine. AE2 mRNA abundance was higher in colon than in more proximal segments. AE2a mRNA was more abundant than AE2b mRNA throughout the intestine, and AE2c mRNA was expressed at very low levels. This AE2 mRNA pattern contrasted with that in mouse stomach, in which AE2c > AE2b > AE2a. AE2 polypeptide abundance as detected by immunoblot qualitatively paralleled that of mRNA, whereas AE2 immunostaining exhibited a more continuous decrease in intensity from colon to duodenum. AE2 polypeptide was more abundant in colonic surface cells than in crypts, whereas ileal crypts and villi exhibited similar AE2 abundance. AE2 was also observed in mural and vascular smooth muscle. Localization of AE2 epitopes was restricted to the basolateral membranes of epithelial cells throughout the intestine with three exceptions. Under mild fixation conditions, anti-AE2 amino acids (aa) 109–122 detected nonpolarized immunostaining of ileal enterocytes and of Paneth cell granule membranes. An epitope detected by anti-AE2 aa 1224–1237 was also localized to subapical regions of Brunner’s gland ducts of duodenum and upper jejunum. These localization studies will aid in the interpretation of anion exchanger function measured in epithelial sheets, isolated cells, and membrane vesicles.