A Golgi study of the cerebral cortex in Fukuyama-type congenital muscular dystrophy, Walker-type "lissencephaly," and classical lissencephaly

Historical review: The golden age of the Golgi method in human neuropathology

Golgi methods were used to study human neuropathology in the 1970s, 1980s, and 1990s of the last century. Although a relatively small number of laboratories applied these methods, their impact was crucial by increasing knowledge about: (1) the morphology, orientation, and localization of neurons in human cerebral and cerebellar malformations and ganglionic tumors, and (2) the presence of abnormal structures including large and thin spines (spine dysgenesis) in several disorders linked to mental retardation, focal enlargements of the axon hillock and dendrites (meganeurites) in neuronal storage diseases, growth cone-like appendages in Alzheimer disease, as well as abnormal structures in other dementias. Although there were initial concerns about their reliability, reduced dendritic branches and dendritic spines were identified as common alterations in mental retardation, dementia, and other pathological conditions. Similar observations in appropriate experimental models have supported many abnormalities that were first identified using Golgi methods in human material. Moreover, electron microscopy, immunohistochemistry, fluorescent tracers, and combined methods have proven the accuracy of pioneering observations uniquely visualized as 3D images of fully stained individual neurons. Although Golgi methods had their golden age many years ago, these methods may still be useful complementary tools in human neuropathology.

Fukutin regulates tau phosphorylation and synaptic function: Novel properties of fukutin in neurons

Fukutin, a product of the causative gene of Fukuyama congenital muscular dystrophy (FCMD), is known to be responsible for basement membrane formation. Patients with FCMD exhibit not only muscular dystrophy but also central nervous system abnormalities, including polymicrogyria and neurofibrillary tangles (NFTs) in the cerebral cortex. The formation of NFTs cannot be explained by basement membrane disorganization. To determine the involvement of fukutin in the NFT formation, we performed molecular pathological investigations using autopsied human brains and cultured neurons of a cell line (SH-SY5Y). In human brains, NFTs, identified with an antibody against phosphorylated tau (p-tau), were observed in FCMD patients but not age-matched control subjects and were localized in cortical neurons lacking somatic immunoreactivity for glutamic acid decarboxylase (GAD), a marker of inhibitory neurons. In FCMD brains, NFTs were mainly distributed in lesions of polymicrogyria. Immunofluorescence staining revealed the colocalization of immunoreactivities for p-tau and phosphorylated glycogen synthase kinase-3β (GSK-3β), a potential tau kinase, in the somatic cytoplasm of SH-SY5Y cells; both the immunoreactivities were increased by fukutin knockdown and reduced by fukutin overexpression. Western blot analysis using SH-SY5Y cells revealed consistent results. Enzyme-linked immunosorbent assay (ELISA) confirmed the binding affinity of fukutin to tau and GSK-3β in SH-SY5Y cells. In the human brains, the density of GAD-immunoreactive neurons in the frontal cortex was significantly higher in the FCMD group than in the control group. GAD immunoreactivity on Western blots of SH-SY5Y cells was significantly increased by fukutin knockdown. On immunofluorescence staining, immunoreactivities for fukutin and GAD were colocalized in the somatic cytoplasm of the human brains and SH-SY5Y cells, whereas those for fukutin and synaptophysin were colocalized in the neuropil of the human brains and the cytoplasm of SH-SY5Y cells. ELISA confirmed the binding affinity of fukutin to GAD and synaptophysin in SH-SY5Y cells. The present results provide in vivo and in vitro evidence for novel properties of fukutin as follows: (i) there is an inverse relationship between fukutin expression and GSK-3β/tau phosphorylation in neurons; (ii) fukutin binds to GSK-3β and tau; (iii) tau phosphorylation occurs in non-GAD-immunoreactive neurons in FCMD brains; (iv) neuronal GAD expression is upregulated in the absence of fukutin; and (v) fukutin binds to GAD and synaptophysin in presynaptic vesicles of neurons.

The classification of cortical dysplasias through molecular genetics

Recent genetic insight into the mechanisms of human brain malformation have allowed one to consider a classification of these disorders by the genetic disruption. In this article an attempt is made to classify human cortical dysplasias by the known genetic disruptions or insults that lead to them. The discussion of malformation is within the context of the embryologic processes that have thought to have gone awry. Human disorders of segmentation, cell proliferation, telencephalic cleavage, differentiation, and neuronal migration are discussed. As this is a rapidly changing area, the reader is encouraged to check online databases for updates on the genetic insights that have been gained since the publication of this article.

Brain development and the genetics of brain development

The progress made in the understanding of the genetics of human brain malformations has lead to insight into the formation of brain and into mechanisms of disease affecting brain. It bears upon neurologists and geneticists to recognize the patterns of diseases of brain formation, to properly diagnose such disorders, to assess the recurrence risk of these malformations, and to guide families with appropriate expectations for outcomes. This article may serve as a guide to neurologists in their approach to these disorders. Because this area is one of rapid progress, the clinician is advised to seek more current information that may be available through on-line databases and other sources.

Topographical features of the sensory-evoked responses in malformed brains

To reveal the functional organization of the somatosensory area in the dysgenetic cortex, somatosensory-evoked potentials were examined in seven patients with congenital brain anomalies diagnosed by magnetic resonance imaging, including six patients in whom multichannel recordings over the scalp were used. In four patients with polymicrogyria/pachygyria and two with lissencephaly, the early cortical responses, frontal P20 and parietal N20, were absent in the cortex contralateral to the stimulated side. The first cortical response was a positive wave that appeared predominantly over the centroparietal area in five patients, and in the frontal area in the other patient with polymicrogyria/pachygyria. These findings suggest that the differentiated somatosensory function is distributed normally in the centroparietal cortex in most cases of widespread cortical dysplasia. However, the absence of P20/N20 may indicate a hypoplastic central sulcus or functionally undifferentiated subdivision of the somatosensory cortex in these patients. The absence of cortical responses in the patient with holoprosencephaly may correspond with growth failure of the thalamocortical afferent projections in this disorder.

Merosin-negative congenital muscular dystrophy, occipital epilepsy with periodic spasms and focal cortical dysplasia. Report of three Italian cases in two families

We report clinical, EEG and neuroimaging findings of three patients in two Italian families with merosin-negative congenital muscular dystrophy (CMD), drug-resistant occipital epilepsy, diffuse persistent cerebral white matter changes and focal cortical dysplasia. Clinical and epilepsy histories, EEG and neuroimaging findings were very similar in all patients. Seizures started in childhood and mainly consisted of periodic spasms, a particular type of partial seizure characterized by clusters of epileptic spasms. The motor expression of the spasms was very mild so that they had been frequently missed or misinterpreted as non-convulsive generalized absence seizures. Interictal EEG showed occipital spike-waves and bilateral synchronous slow spike-wave discharges. Ictal EEG showed prolonged periodic sequences of slow waves with associated fast rhythm complexes, characteristic of periodic spasms. Two patients had normal intelligence, one patient presented moderate mental retardation. Focal cortical dysplasia in the posterior areas of the brain, in addition to marked diffuse white matter alterations, was detected in the magnetic resonance images of all patients. Findings in these patients indicate that in merosin-negative CMD brain involvement can include cortical dysplasia, in addition to white matter changes. In such cases the brain damage can lead to a childhood-onset localization-related symptomatic occipital epilepsy. Epileptic seizures and cortical dysplasia can be, however, difficult to detect in CMD. The clinical semiology of epileptic seizures may in fact be modified because of muscular weakness. This implies that epilepsy may be misdiagnosed or even missed and EEG-polymyographic recordings may be necessary to identify it. Similarly, cortical dysplasia may be very localized and visible by neuroimaging only if it is carefully investigated on the basis of epileptological and EEG-polymyographic findings.

Aberrant neuronal development in hemimegalencephaly: immunohistochemical and Golgi studies

Immunohistochemical and Golgi studies were performed on 6 patients with hemimegalencephaly. Immunohistochemical staining demonstrated glial, neuronal, and myelin heterotopia in the leptomeninges, cortex, and white matter with glial fibrillary acidic protein, myelin basic protein, and synaptophysin antisera. Golgi studies revealed small and deformed neurons in the superficial layers around abnormal sulci, and hypertrophic neurons with an increased number of dendrites and spines in the deeper cortex. The coexistence of a cell migration disorder, proliferation, and hypertrophy in each patient may imply a growth factor disturbance that controls cell proliferation. These unilateral cerebral malformations suggest that early surgical excision may be beneficial.

Synaptic dysgenesis

Synapse formation is a complex, incompletely understood process that has received only limited investigation in man despite the importance of synaptic dysfunction in common disorders such as epilepsy and mental retardation. This review explores synaptic differentiation, focussing on the morphologic maturation of synapses. Since differentiation depends on many antecedent developmental events, synaptogenesis can be affected by several factors: errors in neuronal proliferation, migration, and differentiation. The challenge to the neurobiologist is to detect and evaluate the minor alterations in neuronal differentiation that could account for the structural basis of the clinical manifestations. Trisomy 21 is an example of a condition in which the cytoarchitecture of the cerebral cortex is not obviously altered, yet mental retardation is consistently present; research neurobiologic techniques are making possible documentation of its structural basis. Epilepsy is another example in which examination of surgically removed cerebral cortex reveals subtle cortical dysplasias helpful in understanding the basis for the abnormal electrical discharge. Further exploration of synaptogenesis, particularly the influence of gene products and epigenetic factors on synapse maturation, will increase our understanding of the pathogenesis of conditions in which "morphology" seems normal but function is abnormal.

Structure in lissencephaly determined by immunohistochemical staining

The brains of patients with lissencephaly were examined by peroxidase-antiperoxidase immunohistochemical staining of synaptophysin, myelin basic protein, and glial fibrillary acidic protein. In contrast to the normal cortical pattern, the cortex, with a smooth surface, demonstrated quite different staining patterns in the molecular, superficial cellular, sparsely cellular, and deep cellular layers. The molecular layer was abnormally positive with synaptophysin staining. The superficial cellular layer was also diffusely stained for synaptophysin; there was a positive reaction in the linearly arranged myelin sheaths. The sparsely cellular layer revealed less staining for synaptophysin, but was perivascularly positive for glial fibrillary acidic protein. In the deep cellular layer, synaptophysin staining had multiple neuronal columns and myelin basic protein-staining had a reticular pattern around neuronal columns. These results suggest that the sparsely cellular layer may correspond to the molecular layer and white matter in normal brain; neurons with forming myelin sheaths in the superficial cellular layer regularly penetrate the surface of the molecular layer, forming arrested cortical columns in the deep cellular layer.

Walker-Warburg syndrome in a Japanese patient

We report the first Japanese female patient with Walker-Warburg syndrome. She had generalized muscle hypotonia with hydrocephalus due to Dandy-Walker malformation and bilateral microphthalmia with opaque corneas. She had severe motor and mental retardation. Muscle histology reflected advanced changes of muscular dystrophy. We discuss the relationship between Fukuyama congenital muscular dystrophy and Walker-Warburg syndrome, both of which fall within a spectrum of developmental abnormalities with a common cause. In Fukuyama congenital muscular dystrophy, ocular abnormalities are less severe.