02679nas a2200241   4500008004100000022002500041245011900066210006900185260001600254300000900270520193000279653001602209653002402225653001602249653001202265653002002277653001602297100001802313700001602331700002202347700002102369856004702390       2024                        eng d  a0302-766X, 1432-087800aOrganization of the stalk system on electrocytes in mormyrid weakly electric fish Campylomormyrus compressirostris0 aOrganization of the stalk system on electrocytes in mormyrid wea  cDec-20-2024  a1-173 a<p><jats p="">The adult electric organ in weakly electric mormyrid fish consists of action-potential-generating electrocytes, structurally and functionally modified skeletal muscle cells. The electrocytes have a disc-shaped portion and, on one of its sides, numerous thin processes, termed stalklets. These unite to stalks leading to a single main stalk that carries the innervation site. Here, we describe the 3-dimensional layout of the stalklet/stalk system in adult <jats italic=""><em>Campylomormyrus compressirostris</em></jats> by differential interference contrast microscopy and confocal fluorescence microscopy. Using antibodies against Na<jats sup="">+</jats>/K<jats sup="">+</jats>-ATPase &alpha;-subunit and plasma membrane Ca<jats sup="">2+</jats>-ATPase, we show that these ion pumps are differentially distributed over the stalklet/stalk system, with plasma membrane Ca<jats sup="">2+</jats>-ATPase being enriched on the stalklet membrane. Stalklets are distributed and organized in a quite uniform pattern on the posterior face of the electrocyte disc and fuse to terminal stalks. The latter then unite in a mostly dichotomic mode to stalks of increasing thickness, with the main stalk measuring about 100&nbsp;&micro;m in diameter. We further analyse the structural organization of stalklets and stalks, with a characteristic cytoskeletal system of bundled actin filaments in the centre and nuclei in subsurface position. These results suggest that the stalklet/stalk system is adapted in its structural layout to generate an action potential highly synchronized over the entire disc-portion of the electrocyte, accounting for the short electric organ discharge in this species. Our results suggest that actin-related proteins overexpressed in electrocytes, as shown previously by transcriptome analysis, may be involved in the organization of the unique F-actin system in stalklets and stalks.</jats></p>
10aCa2+-ATPase10aConfocal microscopy10aelectrocyte10aF-actin10aPlasma membrane10aSodium pump1 aBaumann, Otto1 aCheng, Feng1 aKirschbaum, Frank1 aTiedemann, Ralph  uhttps://doi.org/10.1007/s00441-024-03938-y