Merosin-positive congenital muscular dystrophy with mental retardation, microcephaly and central nervous system abnormalities unlinked to the Fukuyama muscular dystrophy and muscular-eye-brain loci: report of three siblings

Optimizing Embryo Collection for Application of CRISPR/Cas9 System and Generation of Fukutin Knockout Rat Using This Method

Rat animal models are widely used owing to their relatively superior cognitive abilities and higher similarity compared with mouse models to human physiological characteristics. However, their use is limited because of difficulties in establishing embryonic stem cells and performing genetic modifications, and insufficient embryological research. In this study, we established optimal superovulation and fertilized-egg transfer conditions, including optimal hormone injection concentration (≥150 IU/kg of PMSG and hCG) and culture medium (mR1ECM), to obtain high-quality zygotes and establish in vitro fertilization conditions for rats. Next, sgRNA with optimal targeting activity was selected by performing PCR analysis and the T7E1 assay, and the CRISPR/Cas9 system was used to construct a rat model for muscular dystrophy by inducing a deficiency in the fukutin gene without any off-target effect detected. The production of fukutin knockout rats was phenotypically confirmed by observing a drop-in body weight to one-third of that of the control group. In summary, we succeeded in constructing the first muscular dystrophy disease rat model using the CRISPR/CAS9 system for increasing future prospects of producing various animal disease models and encouraging disease research using rats.

Abnormal Head Size in Children and Adolescents with Congenital Nervous System Disorders or Neurological Syndromes with One or More Neurodysfunction Visible since Infancy

The current study was designed to investigate co-occurrence of absolute/relative microcephaly, absolute/relative macrocephaly and congenital nervous system disorders or neurological syndromes with symptoms visible since infancy, based on fundamental data acquired during the admission procedure at a neurological rehabilitation ward for children and adolescents. The study applied a retrospective analysis of data collected during the hospitalization of 327 children and adolescents, aged 4-18 years, affected since infancy by congenital disorders of the nervous system and/or neurological syndromes associated with a minimum of one neurodysfunction. To identify subjects with absolute/relative microcephaly, absolute/relative macrocephaly in the group of children and adolescents, the adopted criteria took into account z-score values for head circumference (z-score hc) and head circumference index (z-score HCI). Dysmorphological (x+/-3s) and traditional (x+/-2s) criteria were adopted to diagnose developmental disorders of head size. Regardless of the adopted criteria, absolute macrocephaly often coexists with state after surgery of lumbar myelomeningocele and hydrocephalus, isolated hydrocephalus, hereditary motor and sensory polyneuropathy, and Becker's muscular dystrophy (p < 0.001, p = 0.002). Absolute macrocephaly is often associated with neural tube defects and neuromuscular disorders (p = 0.001, p = 0.001). Relative microcephaly often occurs with non-progressive encephalopathy (p = 0.017, p = 0.029). Absolute microcephaly, diagnosed on the basis of traditional criteria, is often associated with epilepsy (p = 0.043). In children and adolescents with congenital nervous system disorders or neurological syndromes with one or more neurodysfunction visible since infancy, there is variation in abnormal head size (statistically significant relationships and clinical implications were established). The definitions used allowed for the differentiation of abnormal head size.

POMT2 intragenic deletions and splicing abnormalities causing congenital muscular dystrophy with mental retardation

BACKGROUND

Alpha-dystroglycanopathies are a group of congenital muscular dystrophies (CMDs) with autosomal recessive inheritance characterized by abnormal glycosylation of alpha-dystroglycan. Although six genetic causes have been identified (FKTN, POMGNT1, POMT1, POMT2, FKRP, and LARGE) many alpha-dystroglycanopathy patients remain without a genetic diagnosis after standard exon sequencing. To date POMT2 mutations have been identified in CMD cases with a wide range of clinical severities from Walker-Warburg syndrome to limb girdle muscular dystrophy without structural brain or ocular involvement.

METHODS

We analyzed POMT2 in six CMD patients, who had severe diffuse muscle weakness, generalized joint contractures, microcephaly, severe mental retardation and elevated CK levels. Eye involvement was absent or limited to myopia or strabismus. We sequenced the coding regions of POMT2 using genomic DNA and cDNA generated from blood lymphocytes or B lymphoblastoid cell lines. Quantitative PCR analysis of genomic DNA was used to identify and determine the breakpoints of large deletions.

RESULTS

We report five novel mutations in POMT2, four of which were outside of coding exons, two large genomic deletions and two intronic single base substitutions that induced aberrant mRNA splicing.

CONCLUSIONS

Large scale DNA rearrangements (such as large deletions) and cryptic splice mutations, that can be missed on standard sequencing of genomic DNA, may be relatively common in POMT2. Additional techniques, such as sequencing of cDNA are needed to identify all mutations. These results also confirm that POMT2 mutations are an important cause of the less severe alpha-dystroglycanopathy phenotypes.

Congenital muscular dystrophies and the extracellular matrix

During the past decade, considerable progress in the field of congenital muscular dystrophies (CMDs) had led to the identification of a growing number of causative genes. This genetic progress has uncovered crucial pathophysiological concepts and has been instrumental in redefining clinical phenotypes. Important new pathogenic mechanisms include the disorders of O-mannosyl-linked glycosylation of alpha-dystroglycan as well as the involvement of a collagen type VI in the pathogenesis of congenital disorders of muscle. Thus, an emerging theme among gene products involved in the pathogenesis of congenital muscular dystrophy is their intimate connection to the extracellular matrix. In this review, we focus on the clinical phenotypes that we are correlating with the novel genetic and biochemical findings encountered within CMD. This correlation will frequently lead to a considerably expanded clinical spectrum associated with a given CMD gene.

Congenital muscular dystrophy in Arab children

The congenital muscular dystrophies are autosomal recessive disorders with different clinical phenotypes, the spectrum of which varies between different ethnic communities. We report our findings in 21 Arab children with congenital muscular dystrophy. All 21 cases were of the pure type, with normal mental status, except 1 case with perinatal hypoxic-ischemic insult. Fourteen were laminin alpha2 (merosin) deficient, and six were laminin alpha2 positive; laminin alpha2 status was not determined in one patient. None of the laminin alpha2-deficient patients achieved independent ambulation, whereas three of the laminin alpha2-positive patients were able to walk. The elevated levels of serum creatine kinase did not differentiate the two groups and tended to decrease after the age of 5 years. Radiologic evaluation demonstrated an abnormal central white-matter signal in 11 of 13 laminin alpha2-deficient and in 1 of 5 laminin alpha2-positive patients; none had evidence of brain dysplasia. Nerve conduction velocities were normal in 5 of 5 laminin alpha2-positive patients, whereas in the laminin alpha2-deficient patients, it was slow in 9 of 11 for the motor nerves and normal in 8 of 9 for the sensory nerve. Two of the laminin alpha2-positive patients had pseudohypertrophy of the calves, and two of the laminin alpha2-deficient ones had seizures. The patient in whom the laminin alpha2 status was not determined had a severe course, an abnormal central white-matter signal, and epilepsy and resembled more the laminin alpha2-deficient group.

Congenital malformations of the human brainstem

Congenital disorders of the brainstem often result in multiple severe neurodevelopmental problems. With the advent of magnetic resonance imaging and discovery of genes directing brainstem formation, a more coherent clinical picture of these disorders is emerging. Proper evaluation, management, and counseling for these disorders rests on the clinician having a framework through which to approach them.

Congenital muscular dystrophies

The number of new syndromes, loci, and genes responsible for CMD forms has dramatically increased in the last few years, and it has become increasingly evident that the classification of the different forms of CMD is a difficult task. A recent classification separated the forms of CMD that have been mapped (CMD diseases) from the ones with clearly defined clinical and pathologic features that have not been mapped yet (CMD syndromes). Eight CMD forms have been mapped up to now, and the genes responsible for three of them have been identified. This review describes an update of clinical, pathologic, and genetic findings in the different CMD forms.