Single Nucleotide Polymorphisms in the Obscurin Gene and Left Ventricular Hypertrabeculation (Noncompaction)
Josef Finsterer*
Krankenanstalt Rudolfstiftung, Vienna, Austria
*Corresponding
author:
Josef Finsterer, Krankenanstalt Rudolfstiftung, Postfach 20, 1180 Vienna,
Austria. Tel: +4317116592085; Fax: +4314781711; Email: fipaps@yahoo.de
Received Date: 20 August, 2018; Accepted
Date: 07 September, 2018; Published Date: 18 September, 2018
Citation: Finsterer J (2018) Single Nucleotide Polymorphisms in the Obscurin Gene and Left Ventricular Hypertrabeculation (Noncompaction). Cardiolog Res Cardiovasc Med 3: 137. DOI: 10.29011/2575-7083.000037
Keywords: Myopathy;
Neuromuscular; Non-Compaction; Obscurin; Sarcomere
Letter
to the Editor
In an interesting, recent article, Rowland et
al. reported a case study of 4 patients carrying variants in the obscurin gene,
of whom three presented with Left Ventricular Hypertrabeculation /
noncompaction (LVHT) and one with dilated cardiomyopathy [1]. Obscurin plays a key role in
myofibrillogenesis and cytoskeletal arrangement through interaction with titin,
myomesmin, and obscurin-like-1 to generate a complex important for myofibrillar
M-band function. Since the current perception is that contractility of the
heart correlates with non-compaction, a relation between obscurin variants and
LVHT is not surprising. We have the following
comments and concerns.
We do not agree that the association between obscurin
variants and LVHT is “strong” [1]. To demonstrate a
“strong” association higher levels of evidence are required. Though LVHT has
been reported in association with mutations and polymorphisms in >40 genes
and with numerous chromosomal defects, a causal relation has never been proven [2]. Arguments against a causal
relation are that LVHT can be acquired, that in patients with a
dominantly transmitted disease, LVHT may not occur in each generation, that
cardiac abnormalities associated with a given mutation can be highly variable
within a family, that in families with a Neuromuscular Disorder (NMD), LVHT can
be found only in a small number of patients, that the number of mutated genes
claimed to be responsible for the occurrence of LVHT is large, and that LVHT
may not segregate with a specific mutation [3].
Did other first-degree relatives also carry the obscurin variants and did those
carrying the obscurin variants also manifest with LVHT? Arguments in favor of a
causal relation, however, are that LVHT is more frequent in patients carrying
certain genetic defects (e.g. DMPK, TAZ) compared with mutations in other genes [4] and that LVHT has familial occurrence.
We should be
informed whether any of the mutation carriers also had developed myopathy since
up to 80% of the patients with an NMD have LVHT and since obscurin mutations
have been shown to cause myopathy, at least in mice [5].
Altogether, a
causal relation between LVHT and mutations in sarcomeric proteins awaits
confirmation and work-up for LVHT must include a neurological investigation and
investigation of first degree relatives, even if they are asymptomatic. The
reason why obscurin variants were associated with LVHT in 75% of the cases in
Roland’s study and previously, awaits an explanation.
- Rowland TJ, Graw
SL, Sweet ME, Gigli M, Taylor MRG, et al. (2016) Obscurin Variants
in Patients with Left Ventricular Noncompaction. J Am Coll Cardiol
68: 2237-2238.
- Finsterer J, Zarrouk-Mahjoub S (2015)
Considerations about the genetics of left ventricular
hypertrabeculation/non-compaction. Cardiol Young 25: 1435-1437.
- Finsterer J (2009) Cardiogenetics,
neurogenetics, and pathogenetics of left ventricular
hypertrabeculation/noncompaction. Pediatr Cardiol 30: 659-681.
- Finsterer J, Stöllberger C, Towbin JA (2016) Left ventricular
noncompaction. cardiomyopathy: cardiac, neuromuscular, and genetic
implications. Nat Rev Cardiol 14: 224-237.
- Lange S, Ouyang K, Meyer G, Cui L,
Cheng H, et al. (2009) Obscurin determines the architecture of the longitudinal
sarcoplasmic reticulum. J Cell Sci 122: 2640-2650.
- Rowland TJ, Graw SL, Sweet ME, Gigli M, Taylor MRG, et al. (2016) Obscurin Variants in Patients with Left Ventricular Noncompaction. J Am Coll Cardiol 68: 2237-2238.
- Finsterer J, Zarrouk-Mahjoub S (2015) Considerations about the genetics of left ventricular hypertrabeculation/non-compaction. Cardiol Young 25: 1435-1437.
- Finsterer J (2009) Cardiogenetics, neurogenetics, and pathogenetics of left ventricular hypertrabeculation/noncompaction. Pediatr Cardiol 30: 659-681.
- Finsterer J, Stöllberger C, Towbin JA (2016) Left ventricular noncompaction. cardiomyopathy: cardiac, neuromuscular, and genetic implications. Nat Rev Cardiol 14: 224-237.
- Lange S, Ouyang K, Meyer G, Cui L, Cheng H, et al. (2009) Obscurin determines the architecture of the longitudinal sarcoplasmic reticulum. J Cell Sci 122: 2640-2650.