A recurrent single-amino acid deletion (p.Glu500del) in the head domain of ß-cardiac myosin in two unrelated boys presenting with polyhydramnios, congenital axial stiffness and skeletal myopathy.

BACKGROUND: Alterations in the MYH7 gene can cause cardiac and skeletal myopathies. MYH7-related skeletal myopathies are extremely rare, and the vast majority of causal variants in the MYH7 gene are predicted to alter the rod domain of the of ß-cardiac myosin molecule, resulting in distal muscle weakness as the predominant manifestation. Here we describe two unrelated patients harboring an in-frame deletion in the MYH7 gene that is predicted to result in deletion of a single amino acid (p.Glu500del) in the head domain of ß-cardiac myosin. Both patients display an unusual skeletal myopathy phenotype with congenital axial stiffness and muscular hypertonus, but no cardiac involvement. RESULTS: Clinical data, MRI results and histopathological data were collected retrospectively in two unrelated boys (9 and 3.5 years old). Exome sequencing uncovered the same 3-bp in-frame deletion in exon 15 (c.1498_1500delGAG) of the MYH7 gene of both patients, a mutation which deletes a highly conserved glutamate residue (p.Glu500del) in the relay loop of the head domain of the ß-cardiac myosin heavy chain. The mutation occurred de novo in one patient, whereas mosaicism was detected in blood of the father of the second patient. Both boys presented with an unusual phenotype of prenatal polyhydramnios, congenital axial stiffness and muscular hypertonus. In one patient the phenotype evolved into an axial/proximal skeletal myopathy without distal involvement or cardiomyopathy, whereas the other patient exhibited predominantly stiffness and respiratory involvement. We review and compare all patients described in the literature who possess a variant predicted to alter the p.Glu500 residue in the ß-cardiac myosin head domain, and we provide in-silico analyses of potential effects on polypeptide function. CONCLUSION: The data presented here expand the phenotypic spectrum of mutations in the MYH7 gene and have implications for future diagnostics and therapeutic approaches.

GSBF1, a seedling-specific bZIP DNA-binding protein with preference for a 'split' G-box-related element in Brassica napus RbcS promoters.

Promoters of RbcS genes may contain a GS-box, which is a cis element with a core sequence related to the G-box, but split by a spacer of about 14 bp. Here we describe GSBF1, a DNA-binding protein that specifically interacts with a GS-box element located proximal to the G-box in the Brassica napus RbcS IV promoter. Sequence analysis of GSBF1 revealed a basic region/leucine zipper (bZIP) domain that displays structural features distinct from that of G-box binding factors (GBFs). Gel shift experiments showed that recombinant GSBF1 does not efficiently bind to the continuous G-box motif. RNA gel blot analysis indicated that GSBF1 transcripts are cotyledon-specific and accumulate to the highest levels during late seedling development in a ligh-dependent manner. During the same time period, RbcS IV transcript levels decreased simultaneously, suggesting that GSBF1 acts as a developmental, stage-specific, negative regulator of RbcS IV gene expression in rape seedlings.

Sequence and expression characteristics of three G-box-binding factor cDNAs from Brassica napus [corrected].

G-box-binding factors (GBFs) are bZIP proteins that have been implicated in the transcriptional control of a number of plant genes including the family for the small subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase. Using rbcS promoter regions as recognition site probes, we have cloned three Brassica GBFs designated as BnGBF1a, 1b and 2a. RNA gel blot analyses showed that all three BnGBF sequences give transcripts of the same size (1.3 kb) but in different amounts at a constant ratio in various tissues and developmental stages (1a > 2a > 1b). Transcript pools were largest in photosynthetically active organs such as leaves and cotyledons. Pool sizes correlated with those of total rbcS transcripts.