Fukuyama-type congenital muscular dystrophy and the Walker-Warburg syndrome

Genetic defects disrupting glial ion and water homeostasis in the brain

Electrical activity of neurons in the brain, caused by the movement of ions between intracellular and extracellular compartments, is the basis of all our thoughts and actions. Maintaining the correct ionic concentration gradients is therefore crucial for brain functioning. Ion fluxes are accompanied by the displacement of osmotically obliged water. Since even minor brain swelling leads to severe brain damage and even death, brain ion and water movement has to be tightly regulated. Glial cells, in particular astrocytes, play a key role in ion and water homeostasis. They are endowed with specific channels, pumps and carriers to regulate ion and water flow. Glial cells form a large panglial syncytium to aid the uptake and dispersal of ions and water, and make extensive contacts with brain fluid barriers for disposal of excess ions and water. Genetic defects in glial proteins involved in ion and water homeostasis disrupt brain functioning, thereby leading to neurological diseases. Since white matter edema is often a hallmark disease feature, many of these diseases are characterized as leukodystrophies. In this review we summarize our current understanding of inherited glial diseases characterized by disturbed brain ion and water homeostasis by integrating findings from MRI, genetics, neuropathology and animal models for disease. We discuss how mutations in different glial proteins lead to disease, and highlight the similarities and differences between these diseases. To come to effective therapies for this group of diseases, a better mechanistic understanding of how glial cells shape ion and water movement in the brain is crucial.

The corticospinal tract: Evolution, development, and human disorders

The corticospinal tract (CST) plays a major role in cortical control of spinal cord activity. In particular, it is the principal motor pathway for voluntary movements. Here, we discuss: (i) the anatomic evolution and development of the CST across mammalian species, focusing on its role in motor functions; (ii) the molecular mechanisms regulating corticospinal tract formation and guidance during mouse development; and (iii) human disorders associated with abnormal CST development. A comparison of CST anatomy and development across mammalian species first highlights important similarities. In particular, most CST axons cross the anatomical midline at the junction between the brainstem and spinal cord, forming the pyramidal decussation. Reorganization of the pattern of CST projections to the spinal cord during evolution led to improved motor skills. Studies of the molecular mechanisms involved in CST formation and guidance in mice have identified several factors that act synergistically to ensure proper formation of the CST at each step of development. Human CST developmental disorders can result in a reduction of the CST, or in guidance defects associated with abnormal CST anatomy. These latter disorders result in altered midline crossing at the pyramidal decussation or in the spinal cord, but spare the rest of the CST. Careful appraisal of clinical manifestations associated with CST malformations highlights the critical role of the CST in the lateralization of motor control. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 77: 810-829, 2017.

Prenatal US and MR imaging findings of lissencephaly: review of fetal cerebral sulcal development

The cerebral cortex develops in three overlapping stages: cell proliferation, neuronal migration, and cortical organization. Abnormal neuronal migration may result in lissencephaly, which is characterized by either the absence (agyria) or the paucity (pachygyria) of cerebral convolutions. The two main clinicopathologic types of lissencephaly may be differentiated according to their prenatal imaging features. Other cranial and extracranial abnormalities also may occur in association with lissencephaly. The prognosis is often poor, but prenatal diagnosis allows appropriate counseling and optimization of obstetric management. Familiarity with the normal ultrasonographic (US) and magnetic resonance (MR) imaging appearances of the fetal cerebral cortex at various stages of gestation is essential for the early detection of abnormal sulcal development. The primary fissures and sulci that can be examined with prenatal US and MR imaging include the parieto-occipital fissure, calcarine fissure, cingulate sulcus, convexity sulci, and sylvian fissure and insula.

Mutations inPOMT1 are found in a minority of patients with Walker-Warburg syndrome

Walker-Warburg syndrome (WWS) is an autosomal recessive disorder of infancy characterized by hydrocephalus, agyria, retinal dysplasia, congenital muscular dystrophy, and over migration of neurons through a disrupted pial surface resulting in leptomeningeal heterotopia. Although previous work identified mutations in the o-mannosyl transferase, POMT1, in 6 out of 30 WWS families [Beltran-Valero de Bernabe et al., 2002], the incidence of POMT1 mutations in WWS is not known. We sequenced the entire coding region of POMT1 in 30 consecutive, unselected patients with classic WWS. Two novel heterozygous mutations were found in two patients from non-consanguineous parents, whereas 28 other patients failed to show any POMT1 mutations. One patient was found to be heterozygous for a transition, g.1233T > A, which predicts p.Y352X. A second patient was found also to be heterozygous for a transition g.1790C > G, which predicts p.S537R. As an additional determination of the frequency of the POMT1 mutations in WWS, we tested for linkage of WWS to POMT1 in six consanguineous families. All six demonstrated heterozygosity and negative LOD scores at the POMT1 locus. From these data we show that POMT1 is an uncommon cause of WWS, the incidence of coding region mutations in this population of WWS being less than 7%. We conclude that while the incidence of POMT1 mutations in WWS can be as high as 20% as reported by Beltran-Valero de Bernabe et al. [2002] and it can be as low as approximately 7%, as reported here.

Spontaneous cerebellar dysplasias in BrlHan: WIST@Jcl rats

Focal disturbed laminar architecture in cerebellar vermis was observed in 25 out of 100 (25%) males, and 25 out of 100 (25%) females of BrlHan: WIST@Jcl rats. The cortical molecular and granular layers were haphazardly distributed around the primary and/or secondary fissures. The stellate and basket cells positively stained with parvalbumin immunohistochemistry were observed exclusively in the separated molecular layer. Purkinje cells were found at the boundary between the molecular and the granular layers. Glial fibrillary acid protein (GFAP) immunohistochemistry revealed disarranged fibers of the Bergman glial cells. Based on the incidence of this spontaneous cerebellar lesion, it was presumed to be related to certain genetic factors of this rat strain.

Clinicopathological study on eyes from cases of Fukuyama type congenital muscular dystrophy

Fukuyama type congenital muscular dystrophy (FCMD) is an autosomal recessive disorder characterized by progressive muscular dystrophy and dysgenesis of the central nervous system and eyes. To clarify the pathomechanism of the ocular involvement in FCMD, we performed postmortem pathological analyses of eyes from three postnatal FCMD cases, two fetal FCMD cases, and three control cases by macroscopic, histopathological, immunohistochemical and in situ hybridization approaches. The macroscopic and histopathological examinations revealed a variety of ocular abnormalities such as folding, fusion or dysplasia of the retinas in the FCMD cases both with and without ophthalmological alterations. Immunoreactivities for collagen IV and laminin, produced by Müller cells, as the basement membrane components, were less intense in the inner limiting membrane of the FCMD retinas than in that of the control retinas. A number of the perivascular glial cells containing S-100 protein and glial fibrillary acidic protein were increased in the postnatal FCMD cases. Immunoreactivities for vimentin, glutamate transporter-1, glutamine synthase and ornithine aminotransferase, expressed in the Müller cells, were undetectable in the fetal FCMD retinas, and reduced in the postnatal FCMD retinas compared with the control retinas. Fukutin mRNA signals were distributed diffusely in the retinoblast layer of the control retinas, focally in the retinoblast layer of the fetal FCMD retinas, and only in the dysplastic areas with rosette formation of the postnatal FCMD retinas, composed of retinoblasts and other retinal cells including the Müller cells. The present findings suggest that the Müller cells are implicated in the retinal pathology of FCMD.

A case of Walker-Warburg syndrome

Walker-Warburg syndrome (WWS) is an autosomal recessive disorder characterized by type II lissencephaly, cerebellar and retinal anomalies, and congenital muscular dystrophy. We report a female diagnosed with WWS based on clinical criteria. This patient was found to have fetal hydrocephalus on ultrasonography at 29 weeks of gestation, and exhibited severe hypotonia, ocular malformations, and hydrocephalus at birth. MRI revealed type II lissencephaly, hydrocephalus, and other severe brain malformations. Genetic analysis was performed to distinguish WWS from severe Fukuyama-type congenital muscular dystrophy (FCMD), which has numerous findings in common. This revealed no expression of the founder haplotype or single-stranded conformation polymorphism (SSCP) abnormalities. Since the life expectancy of patients with FCMD is longer, differential diagnosis should be performed precisely.

Unreported anatomical variation of septum pellucidum

During gross anatomy dissections of the brain, a developmental abnormality of the septum pellucidum was found in a 31-year-old male cadaver. Other parts of the central nervous system in this cadaver were normal in every aspect. Histological samples were taken from the neighboring areas of this abnormality, and they were examined under light microscope and scanning electron microscope. In this abnormality of the septum pellucidum, the two laminae of the septum pellucidum were fused together and there was a hole located 1 cm anterior to its apex. The maximum diameter of the hole was 0.5 cm in the sagittal plane and 0.6 cm in the vertical plane. In the light microscopic and scanning electron microscopic examinations, the free margin of this foramen was regular, and the surrounding tissue was intact and histologically unique to the septum pellucidum. Ependymal cells were present at the free margin of the foramen. Cavum vergae, cavum septum pellucidum, and agenesis of the septum pellucidum are described in the literature. These three abnormalities are seen in cadavers usually with histories of schizophrenia and other psychiatric or neurologic disorders. In a retrospective study, the cadaver with this abnormality had a history of schizophrenia and no history or signs of any kind of brain or head operation. As far as we could ascertain, the abnormality described here has not been reported previously.

Walker-Warburg syndrome: neurologic features and muscle membrane structure

Walker-Warburg syndrome is an autosomal-recessive genetic disorder characterized by congenital muscular dystrophy in association with complex developmental abnormalities of the central nervous system and the eyes. Two patients with Walker-Warburg syndrome are presented to demonstrate clinical variability. Previously unreported pathologic findings involving heart, muscle, spinal cord, and gall bladder are described, and the literature is reviewed. Histopathologic studies of the muscle membrane protein network in both Walker-Warburg syndrome patients reveal a decreased immunostaining for laminin alpha2 and beta-dystroglycan. The clinical, histologic, and biochemical variability in Walker-Warburg patients may reflect heterogeneity.

Magnetic resonance imaging in classification of congenital muscular dystrophies with brain abnormalities

A survey was performed of magnetic resonance imaging (MRI) findings in 21 patients with congenital muscular dystrophy (CMD) with cerebral abnormalities to evaluate the contribution of MRI to the classification of CMD patients. In 5 patients with Walker-Warburg syndrome (WWS), MRI showed hydrocephalus due to aqueduct stenosis, generalized cerebral cortical agyric or pachygyric polymicrogyria, diffuse cerebral hemispheric white matter abnormalities, and malformations of posterior fossa structures. In 4 patients with muscle-eye-brain disease, MRI showed cortical dysplasia, but less severe than in WWS. The cerebral white matter either was normal or contained multiple focal abnormalities. Malformations of posterior fossa structures were present. Eight patients, classified as having classic merosin-deficient CMD (MD-CMD), had diffuse cerebral hemispheric white matter abnormalities, no other abnormalities. One patient with MD-CMD had only a few, focal white matter abnormalities. Three CMD patients had occipital agyria, otherwise normal gyration, multifocal or more diffuse cerebral white matter changes, and variable hypoplasia of pons and vermis. Two of the 3 patients had negative muscle merosin staining. The conclusion of the study is that MRI is an important adjunct in the classification of CMD patients. CMD with occipital agyria can be regarded as a newly recognized, separate CMD subtype.

Congenital muscular dystrophy with severe retrocollis and mental retardation: a report of two siblings

Two siblings with a congenital muscular dystrophy and severe mental retardation which was not due to dystrophin, merosin, or adhalin deficiency are described. These cases overlap with congenital muscular dystrophy of the Fukuyama-type but are less severe. Atypical features include limited facial involvement, retained ambulation, and severe retrocollis.

Congenital muscular dystrophy with cerebral white matter hypodensity. Correlation of clinical features and merosin deficiency

We report clinical and pathological findings in 9 children affected by congenital muscular dystrophy with normal or borderline intelligence and hypodensity of cerebral white matter (CMD-HWM), also frequently called 'occidental or western form of cerebro-muscular dystrophy' (OCMD). Our patients have uniform, distinct, clinical presentation that includes: normal or subnormal intelligence, severe, slowly progressive motor disability, high rate of facial involvement and dysmorphic aspect, increased creatine kinase levels and variable degrees of abnormal, radiographic, cerebral white matter pattern. By comparing our cases with previous reports we suggest that this subtype of CMD is not uncommon in Brazil and it is represented by a particularly severe and homogeneous clinical picture with important motor disability. The immunohistochemical staining for merosin, performed on the muscle biopsy of 6 among 9 patients, showed that all are merosin negative.

Morphometric study of the corpus callosum in Fukuyama type congenital muscular dystrophy by magnetic resonance imaging

The corpus callosum (CC) of 24 Fukuyama type congenital muscular dystrophy (FCMD) patients were studied using midsagittal MRI and the results were compared with those of 20 age-matched controls. The measurements included the thickness of the genu, body and splenium; the length, height and five specific angles of the CC. The cephalic index was also measured on axial MRI. The correlations among CC length, CC height, the five angles and the cephalic index were evaluated. One case of FCMD was found to have CC agenesis. The thickness of the genu, body, splenium and CC length were significantly reduced in FCMD. In addition, in FCMD, the CC height was increased, angle alpha was greater, angle delta reduced and the CC configuration more rounded, showing a high arch on imaging. No significant correlations among CC length, CC height, the five specific angles and the cephalic index were found in any of the FCMD data. These observations demonstrated the fact that CC development in FCMD is uniquely abnormal, and abnormal CC configuration does not have any correlation with altered cephalic index.

Genetic identity of Fukuyama-type congenital muscular dystrophy and Walker-Warburg syndrome

Both Fukuyama-type congenital muscular dystrophy (FCMD) and Walker-Warburg syndrome (WWS) are unusual genetic syndromes consisting of congenital muscular dystrophy and complex malformations of the brain and eye. It has been intensively discussed whether FCMD and WWS belong to the same disease entity or not. We analyzed a family in which 3 siblings were affected with either FCMD or WWS by using polymorphic microsatellites flanking the FCMD locus on chromosome 9q31-33. The results suggested that both FCMD and WWS siblings shared the identical combination of mutations on either allele of the FCMD locus. FCMD and WWS could be "genetically" identical.

Muscle and brain disease: an update

A number of syndromes included under this rubric are considered, and their main features discussed. The congenital muscular dystrophy of the Fukuyama type as it occurs in Japan and in the western world are almost certainly the same condition. The muscle disorder is associated with cerebral lesions which may be due to an arrest of neural migration or to demyelination. Muscle, eye and brain disease, or Santavuori's syndrome, shows ocular abnormalities, as well as those of the muscle and brain, as does the Walker-Warburg syndrome. In the latter disorder the cerebral lesions tend to be more severe, and it is more rapidly fatal. The manifestations of all these syndromes undoubtedly overlap, but there has been controversy on the question of their identity. Are they separate entities, or are they different expressions of a similar genetic disorder? The genes for all these conditions will have to be isolated to see if the different phenotypes are alleles of the same gene, or not. Some of the arguments, for and against, are presented.