Disease relevance of NEBL

• Nebulette was shown to be deleted in DiGeorge Syndrome 2 patients with the proximal deletion of human 10p13-p14 that is associated with cardiac and craniofacial abnormalities [1].

High impact information on NEBL

• Screening of two different cDNA libraries, one prepared from human placenta, the other from human heart, yielded several positive clones that occurred in both searches, including clones coding for cyclophilin, nebulette, and alpha-actinin [2].
• Domain-based analyses have recently categorized this protein as an epithelial representative of the nebulin family, which also includes the actin binding, muscle-specific proteins, nebulin, nebulette and N-RAP [3].
• Targeted disruption of nebulette protein expression alters cardiac myofibril assembly and function [4].
• This leads to a substantial diversity of nebulin and nebulette isoforms [5].
• Gene mapping studies assign the human nebulette gene to chromosome 10p12, whereas the nebulin gene has been previously assigned to 2q21 [5].

Biological context of NEBL

• LASP2 mRNA consists of exons 1a-4a, 24, 27, and 28 of the LASP2/NEBL gene, while NEBL mRNA consists of exons 1-28 [6].
• LASP2 and NEBL mRNAs were transcribed from the LASP2/NEBL gene on human chromosome 10p12 due to alternative splicing [6].
• Determination of the complete primary structure of 1011 residue human fetal nebulette reveals a four-domain layout similar to skeletal muscle nebulin: a short N-terminal domain, followed by 22 nebulin-like repeats that are linked to a C-terminal Src homology 3 (SH3) domain via a short linker domain [7].
• The C-terminal regions of nebulin and nebulette are identical in domain organization and share a family of highly related C-terminal repeats, a serine-rich domain with potential phosphorylation sites, and an SH3 domain [5].
• We demonstrate that nebulette is indeed associated with premyofibrils in very early stages of myofibrillogenesis and suggest that nebulette may play an important role in the formation of these structures [8].

Anatomical context of NEBL

• To distinguish this petite nebulin-like protein from the 600-900 kD skeletal muscle nebulin, we have named it nebulette [9].
• Nebulette, a 107 kDa protein associated with the I-Z-I complex of cardiac myofibrils, may play an important role in the assembly of the Z-line [7].
• Nebulette: a 107 kD nebulin-like protein in cardiac muscle [9].
• To elucidate the mechanisms of assembly for nebulette in the Z-line, the complete coding sequence or fusions of nebulette domains with green fluorescent protein (GFP) were expressed in cardiomyocytes and fibroblasts [7].
• We also demonstrate that, although the EOM expresses cardiac isoforms of myosin, it does not express nebulette and contains a nebulin isoform with a mass consistent with that found in the prototypical fast hindlimb muscle EDL [10].

Associations of NEBL with chemical compounds

• The serine-rich linker region of nebulette has previously been shown to serve just such a purpose by targeting the association of the nebulin modules to the cardiac Z-line in cultured cardiomyocytes [11].

Physical interactions of NEBL

• Functional dissection of nebulette demonstrates actin binding of nebulin-like repeats and Z-line targeting of SH3 and linker domains [7].

Co-localisations of NEBL

• Taken together with the observation that nebulette colocalizes with alpha-actinin in the pre-, nascent, and mature myofibrils, our data demonstrate the importance of this cardiac-specific nebulin isoform in myofibril organization and function [4].

Other interactions of NEBL

• Surprisingly, the BAC clone RP11-56H7 that contains NEBL, an apparent downstream gene of the cardiogenic transcription factor HAND2 previously shown to be deleted in the patients with DiGeorge 2 syndrome and 10p13 deletion, was deleted in our patient with 10p12.1-p12.31 deletion [12].
• Supporting the cellular localization work, recombinant nebulette fragments bind to actin, tropomyosin, and alpha-actinin in in vitro binding assays [7].
• The family members now include nebulin, nebulette, N-RAP, LASP-1, and LIM-nebulette [11].
• This interesting mixture of myofibrillar and cytoskeletal proteins poses the questions as to whether nebulette, as opposed to nebulin, might be expressed in EOM, and what isoforms of titin are expressed in the EOM [10].
• Characterization of the human nebulette gene: a polymorphism in an actin-binding motif is associated with nonfamilial idiopathic dilated cardiomyopathy [13].

Analytical, diagnostic and therapeutic context of NEBL

• Immunoelectron-microscopy suggests that the C-terminal 30 kDa of nebulin and nebulette filaments integrate into the Z-disc lattice, whereas their N termini appear to project into the I-band [5].
• To evaluate the role of nebulette in myofibrillogenesis, we have analyzed the expression of nebulette in chicken heart rudiments by immunoblots and immunofluorescence [8].

References