Thin filament length in the cardiac sarcomere varies with sarcomere length but is independent of titin and nebulin

Justin Kolb, Frank Li, Mei Methawasin, Maya Adler, Yael Natalie Escobar, Joshua Nedrud, Christopher T. Pappas, Samantha P. Harris, Henk Granzier

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

Thin filament length (TFL) is an important determinant of the force-sarcomere length (SL) relation of cardiac muscle. However, the various mechanisms that control TFL are not well understood. Here we tested the previously proposed hypothesis that the actin-binding protein nebulin contributes to TFL regulation in the heart by using a cardiac-specific nebulin cKO mouse model (αMHC Cre Neb cKO). Atrial myocytes were studied because nebulin expression has been reported to be most prominent in this cell type. TFL was measured in right and left atrial myocytes using deconvolution optical microscopy and staining for filamentous actin with phalloidin and for the thin filament pointed-end with an antibody to the capping protein Tropomodulin-1 (Tmod1). Results showed that TFLs in Neb cKO and littermate control mice were not different. Thus, deletion of nebulin in the heart does not alter TFL. However, TFL was found to be ~ 0.05 μm longer in the right than in the left atrium and Tmod1 expression was increased in the right atrium. We also tested the hypothesis that the length of titin's spring region is a factor controlling TFL by studying the Rbm20ΔRRM mouse which expresses titins that are ~ 500 kDa (heterozygous mice) and ~ 1000 kDa (homozygous mice) longer than in control mice. Results revealed that TFL was not different in Rbm20ΔRRM mice. An unexpected finding in all genotypes studied was that TFL increased as sarcomeres were stretched (~ 0.1 μm per 0.35 μm of SL increase). This apparent increase in TFL reached a maximum at a SL of ~ 3.0 μm where TFL was ~ 1.05 μm. The SL dependence of TFL was independent of chemical fixation or the presence of cardiac myosin-binding protein C (cMyBP-C). In summary, we found that in cardiac myocytes TFL varies with SL in a manner that is independent of the size of titin or the presence of nebulin.

Original languageEnglish (US)
Pages (from-to)286-294
Number of pages9
JournalJournal of Molecular and Cellular Cardiology
Volume97
DOIs
StatePublished - Aug 1 2016

Fingerprint

Connectin
Sarcomeres
Tropomodulin
Heart Atria
Muscle Cells
Cardiac Myosins
Phalloidine
Microfilament Proteins
nebulin
Cardiac Myocytes
Actins
Microscopy
Myocardium
Genotype
Staining and Labeling
Antibodies

Keywords

  • Cardiac myocyte
  • Length regulation
  • Myofilament
  • Nebulin
  • Thin filament
  • Titin

ASJC Scopus subject areas

  • Molecular Biology
  • Cardiology and Cardiovascular Medicine

Cite this

Thin filament length in the cardiac sarcomere varies with sarcomere length but is independent of titin and nebulin. / Kolb, Justin; Li, Frank; Methawasin, Mei; Adler, Maya; Escobar, Yael Natalie; Nedrud, Joshua; Pappas, Christopher T.; Harris, Samantha P.; Granzier, Henk.

In: Journal of Molecular and Cellular Cardiology, Vol. 97, 01.08.2016, p. 286-294.

Research output: Contribution to journalArticle

Kolb, Justin ; Li, Frank ; Methawasin, Mei ; Adler, Maya ; Escobar, Yael Natalie ; Nedrud, Joshua ; Pappas, Christopher T. ; Harris, Samantha P. ; Granzier, Henk. / Thin filament length in the cardiac sarcomere varies with sarcomere length but is independent of titin and nebulin. In: Journal of Molecular and Cellular Cardiology. 2016 ; Vol. 97. pp. 286-294.
@article{d5e3dcadd10241218c610c0f9ef8dc54,
title = "Thin filament length in the cardiac sarcomere varies with sarcomere length but is independent of titin and nebulin",
abstract = "Thin filament length (TFL) is an important determinant of the force-sarcomere length (SL) relation of cardiac muscle. However, the various mechanisms that control TFL are not well understood. Here we tested the previously proposed hypothesis that the actin-binding protein nebulin contributes to TFL regulation in the heart by using a cardiac-specific nebulin cKO mouse model (αMHC Cre Neb cKO). Atrial myocytes were studied because nebulin expression has been reported to be most prominent in this cell type. TFL was measured in right and left atrial myocytes using deconvolution optical microscopy and staining for filamentous actin with phalloidin and for the thin filament pointed-end with an antibody to the capping protein Tropomodulin-1 (Tmod1). Results showed that TFLs in Neb cKO and littermate control mice were not different. Thus, deletion of nebulin in the heart does not alter TFL. However, TFL was found to be ~ 0.05 μm longer in the right than in the left atrium and Tmod1 expression was increased in the right atrium. We also tested the hypothesis that the length of titin's spring region is a factor controlling TFL by studying the Rbm20ΔRRM mouse which expresses titins that are ~ 500 kDa (heterozygous mice) and ~ 1000 kDa (homozygous mice) longer than in control mice. Results revealed that TFL was not different in Rbm20ΔRRM mice. An unexpected finding in all genotypes studied was that TFL increased as sarcomeres were stretched (~ 0.1 μm per 0.35 μm of SL increase). This apparent increase in TFL reached a maximum at a SL of ~ 3.0 μm where TFL was ~ 1.05 μm. The SL dependence of TFL was independent of chemical fixation or the presence of cardiac myosin-binding protein C (cMyBP-C). In summary, we found that in cardiac myocytes TFL varies with SL in a manner that is independent of the size of titin or the presence of nebulin.",
keywords = "Cardiac myocyte, Length regulation, Myofilament, Nebulin, Thin filament, Titin",
author = "Justin Kolb and Frank Li and Mei Methawasin and Maya Adler and Escobar, {Yael Natalie} and Joshua Nedrud and Pappas, {Christopher T.} and Harris, {Samantha P.} and Henk Granzier",
year = "2016",
month = "8",
day = "1",
doi = "10.1016/j.yjmcc.2016.04.013",
language = "English (US)",
volume = "97",
pages = "286--294",
journal = "Journal of Molecular and Cellular Cardiology",
issn = "0022-2828",
publisher = "Academic Press Inc.",

}

TY - JOUR

T1 - Thin filament length in the cardiac sarcomere varies with sarcomere length but is independent of titin and nebulin

AU - Kolb, Justin

AU - Li, Frank

AU - Methawasin, Mei

AU - Adler, Maya

AU - Escobar, Yael Natalie

AU - Nedrud, Joshua

AU - Pappas, Christopher T.

AU - Harris, Samantha P.

AU - Granzier, Henk

PY - 2016/8/1

Y1 - 2016/8/1

N2 - Thin filament length (TFL) is an important determinant of the force-sarcomere length (SL) relation of cardiac muscle. However, the various mechanisms that control TFL are not well understood. Here we tested the previously proposed hypothesis that the actin-binding protein nebulin contributes to TFL regulation in the heart by using a cardiac-specific nebulin cKO mouse model (αMHC Cre Neb cKO). Atrial myocytes were studied because nebulin expression has been reported to be most prominent in this cell type. TFL was measured in right and left atrial myocytes using deconvolution optical microscopy and staining for filamentous actin with phalloidin and for the thin filament pointed-end with an antibody to the capping protein Tropomodulin-1 (Tmod1). Results showed that TFLs in Neb cKO and littermate control mice were not different. Thus, deletion of nebulin in the heart does not alter TFL. However, TFL was found to be ~ 0.05 μm longer in the right than in the left atrium and Tmod1 expression was increased in the right atrium. We also tested the hypothesis that the length of titin's spring region is a factor controlling TFL by studying the Rbm20ΔRRM mouse which expresses titins that are ~ 500 kDa (heterozygous mice) and ~ 1000 kDa (homozygous mice) longer than in control mice. Results revealed that TFL was not different in Rbm20ΔRRM mice. An unexpected finding in all genotypes studied was that TFL increased as sarcomeres were stretched (~ 0.1 μm per 0.35 μm of SL increase). This apparent increase in TFL reached a maximum at a SL of ~ 3.0 μm where TFL was ~ 1.05 μm. The SL dependence of TFL was independent of chemical fixation or the presence of cardiac myosin-binding protein C (cMyBP-C). In summary, we found that in cardiac myocytes TFL varies with SL in a manner that is independent of the size of titin or the presence of nebulin.

AB - Thin filament length (TFL) is an important determinant of the force-sarcomere length (SL) relation of cardiac muscle. However, the various mechanisms that control TFL are not well understood. Here we tested the previously proposed hypothesis that the actin-binding protein nebulin contributes to TFL regulation in the heart by using a cardiac-specific nebulin cKO mouse model (αMHC Cre Neb cKO). Atrial myocytes were studied because nebulin expression has been reported to be most prominent in this cell type. TFL was measured in right and left atrial myocytes using deconvolution optical microscopy and staining for filamentous actin with phalloidin and for the thin filament pointed-end with an antibody to the capping protein Tropomodulin-1 (Tmod1). Results showed that TFLs in Neb cKO and littermate control mice were not different. Thus, deletion of nebulin in the heart does not alter TFL. However, TFL was found to be ~ 0.05 μm longer in the right than in the left atrium and Tmod1 expression was increased in the right atrium. We also tested the hypothesis that the length of titin's spring region is a factor controlling TFL by studying the Rbm20ΔRRM mouse which expresses titins that are ~ 500 kDa (heterozygous mice) and ~ 1000 kDa (homozygous mice) longer than in control mice. Results revealed that TFL was not different in Rbm20ΔRRM mice. An unexpected finding in all genotypes studied was that TFL increased as sarcomeres were stretched (~ 0.1 μm per 0.35 μm of SL increase). This apparent increase in TFL reached a maximum at a SL of ~ 3.0 μm where TFL was ~ 1.05 μm. The SL dependence of TFL was independent of chemical fixation or the presence of cardiac myosin-binding protein C (cMyBP-C). In summary, we found that in cardiac myocytes TFL varies with SL in a manner that is independent of the size of titin or the presence of nebulin.

KW - Cardiac myocyte

KW - Length regulation

KW - Myofilament

KW - Nebulin

KW - Thin filament

KW - Titin

UR - http://www.scopus.com/inward/record.url?scp=84978198941&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84978198941&partnerID=8YFLogxK

U2 - 10.1016/j.yjmcc.2016.04.013

DO - 10.1016/j.yjmcc.2016.04.013

M3 - Article

C2 - 27139341

AN - SCOPUS:84978198941

VL - 97

SP - 286

EP - 294

JO - Journal of Molecular and Cellular Cardiology

JF - Journal of Molecular and Cellular Cardiology

SN - 0022-2828

ER -