Idiopathic intracranial hypertension and facial diplegia.
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Acetazolamide↗
Biomedical subjects
W B Dobyns
Publications and source records attributed to W B Dobyns.
Lissencephaly. A human brain malformation associated with deletion of the LIS1 gene located at chromosome 17p13.
OBJECTIVE: We review the clinical phenotype, pathological changes, and results of cytogenetic and molecular genetic studies in 90 probands with lissencephaly (smooth brain) with emphasis on patients with the classical form (type I). We also describe the recent discovery of the lissencephaly gene (LIS1), deletions of which have been implicated as the cause of this disorder in many patients. DATA SOURCES: We have performed clinical, cytogenetic, and molecular genetic studies of 25 probands with Miller-Dieker syndrome and 65 probands with isolated lissencephaly sequence (ILS). We have further subdivided patients with ILS into those with classical lissencephaly and those with lissencephaly variants. STUDY SELECTION: We consider primarily our own published and unpublished data, but include references to studies of other series of patients with lissencephaly. DATA SYNTHESIS: Visible cytogenetic deletions of 17p13.3 were detected in 14 of 25 Miller-Dieker syndrome probands, and either visible cytogenetic or submicroscopic deletions in 23 (92%) of 25. Submicroscopic deletions were detected in eight of 45 patients with all types of ILS. If only ILS patients with the classical form are considered, we detected deletions in eight (38%) of 21. CONCLUSIONS: Deletions of the lissencephaly critical region in chromosome 17p13.3, including LIS1, appear to be the most frequent cause of classical lissencephaly. Molecular cytogenetic studies, particularly fluorescence in situ hybridization, should be performed in all such patients. LIS1 shows homology to genes involved in signal transduction, which may be its function in development of the telencephalon. Other genetic causes of classical lissencephaly and genetic and nongenetic causes of other types of lissencephaly exist and are under study.
Brain↗
Familial remitting chorea, nystagmus, and cataracts.
We report on 2 brothers with chorea and monocular horizontal nystagmus beginning in early infancy, both of which remit during the first decade of life, and peripheral cataracts. While this condition shares manifestations with benign hereditary chorea and several other familial movement disorders, the slowly remitting course of the chorea combined with the visual abnormalities appears to be unique.
Cataract↗
Isolation of a Miller-Dieker lissencephaly gene containing G protein beta-subunit-like repeats.
Lissencephaly (agyria-pachygyria) is a human brain malformation manifested by a smooth cerebral surface and abnormal neuronal migration. Identification of the gene(s) involved in this disorder would facilitate molecular dissection of normal events in brain development. Type 1 lissencephaly occurs either as an isolated abnormality or in association with dysmorphic facial appearance in patients with Miller-Dieker syndrome. About 15% of patients with isolated lissencephaly and more than 90% of patients with Miller-Dieker syndrome have microdeletions in a critical 350-kilobase region in chromosome 17p13.3 (ref. 6). These deletions are hemizygous, so haplo-insufficiency for a gene in this interval is implicated. Here we report the cloning of a gene (LIS-1, lissencephaly-1) in 17p13.3 that is deleted in Miller-Dieker patients. Non-overlapping deletions involving either the 5' or 3' end of the gene were found in two patients, identifying LIS-1 as the disease gene. The deduced amino-acid sequence shows significant homology to beta-subunits of heterotrimeric G proteins, suggesting that it could possibly be involved in a signal transduction pathway crucial for cerebral development.
Amino Acid Sequence↗
Clinical manifestations and evaluation of isolated lissencephaly.
Lissencephaly ("smooth brain") is a brain malformation characterized by a smooth cerebral surface, incomplete neuronal migration, and secondary abnormalities such as mental retardation, seizures, and minor facial dysmorphisms. Recent reports have produced evidence supporting several different causes including submicroscopic deletions in chromosome band 17p13.3, autosomal recessive inheritance, intrauterine infection, and intrauterine perfusion failure. We describe the clinical manifestations in seven patients with lissencephaly, and review pertinent studies regarding possible causes. The clinical manifestations were uniformly severe. All patients had severe mental retardation, hypotonia, often combined with spastic paralysis, and infantile spasms which did not respond to treatment. Most had poor growth, postnatal microcephaly, feeding problems, and frequent respiratory infections including pneumonia. None had other significant birth defects. Appropriate studies include computed tomography or magnetic resonance imaging (sometimes both), chromosome analysis, DNA analysis of the lissencephaly region on chromosome 17, electroencephalography and sometimes metabolic studies.
Cerebral Cortex↗
Antibodies to ACTH in opsoclonus-myoclonus.
Antibodies to ACTH1-24 detected by radioimmunoassay were present in the serum of a child with opsoclonus-myoclonus for at least 24 weeks after discontinuation of chronic ACTH treatment. The antibody-bound ACTH did not interfere with cortisol secretion. Six other children with opsoclonus-myoclonus and 16 control sera, including patients with chronically elevated endogenous ACTH, did not exhibit autoantibodies to ACTH. Antibodies to ACTH should be sought in patients who develop tolerance to ACTH treatment. The indirect but not direct ACTH assay method is sensitive to the presence of ACTH antibodies.
Adolescent↗
Rapid-onset dystonia-parkinsonism.
We studied a large family with a previously undescribed, autosomal dominant dystonia-parkinsonism syndrome. We chose to call the disorder "rapid-onset dystonia-parkinsonism" (RDP) based on the unusually rapid evolution of signs and symptoms. Affected individuals developed dystonia and parkinsonism between 14 and 45 years of age. The onset was acute in six individuals with the abrupt onset of symptoms over the course of several hours, and subacute in four others who had evolution over several days or weeks. Thereafter, progression of symptoms was usually very slow. Two had intermittent focal dystonia without parkinsonism, and one obligate gene carrier was asymptomatic at 68 years. CSF levels of homovanillic acid were decreased in the two individuals tested, but dopaminergic therapy provided only slight benefit. The DYT1 gene responsible for early-onset, generalized idiopathic torsion dystonia in Jewish and some non-Jewish families has been mapped to chromosome 9q34. Linkage analysis with three markers near the DYT1 gene showed several obligate recombinations, excluding DYT1 as a candidate gene for RDP. We believe RDP is unique and should be classified separately from other forms of hereditary dystonia-parkinsonism.
Adolescent↗
Mechanisms of interhemispheric transfer and patterns of cognitive function in acallosal patients of normal intelligence.
We investigated interhemispheric transfer and cognitive function in two boys with normal intelligence in whom agenesis of the corpus callosum was identified following minor head trauma. In patient 1, magnetic resonance imaging scan showed agenesis of the corpus callosum and absent anterior commissure. Results of visual interhemispheric transfer tasks suggested degradation in transfer of information to the left hemisphere. Results of a tactile interhemispheric transfer task suggested degradation of access to the right hemisphere. In patient 2, magnetic resonance imaging scan showed agenesis of the corpus callosum and enlarged anterior commissure. Results for both visual and tactile interhemispheric transfer tasks were normal. Dichotic listening tests showed a slight left ear advantage in both patients. These results support the hypothesis that hypertrophy of the anterior commissure is an important mechanism of functional compensation in agenesis of the corpus callosum. However, the relative subtlety of deficits in patient 1 and results of dichotic listening tests support use of other mechanisms as well. No consistent pattern of cognitive deficits was observed.
Agenesis of Corpus Callosum↗
Causal heterogeneity in isolated lissencephaly.
We report clinical, cytogenetic, and molecular studies in 65 patients with isolated lissencephaly sequence (ILS). All had type I lissencephaly of varying severity and a grossly normal cerebellum. Some had additional brain abnormalities. Facial appearance was essentially normal. All had severe to profound mental retardation, seizures, hypotonia that evolved into spasticity, and feeding difficulties. Clinical and laboratory studies demonstrated etiologic heterogeneity. Molecular studies detected microdeletions in chromosome band 17p13.3 in six of 44 patients tested, confirming that deletion of all or part of this "critical region" is the cause of ILS in some cases. There were slightly larger deletions in the same region in a majority of patients with Miller-Dieker syndrome. One patient had an apparently balanced, de novo reciprocal translocation with breakpoints at Xq22 and 2p25. Four sibs from two families had a new, autosomal recessive syndrome of ILS with neonatal death. Other causes supported by clinical observations include autosomal recessive inheritance, intrauterine infection, and intrauterine perfusion failure. Those ILS probands in whom no etiology could be established had 41 sibs of whom three were affected, giving an empiric recurrence risk of 7%.
Brain↗
Microdeletions of chromosome 17p13 as a cause of isolated lissencephaly.
Lissencephaly (agyria-pachygyria) is a brain malformation manifested by a smooth cerebral surface, resulting from arrest of neuronal migration at 10-14 wk gestation. Type I, or classical, lissencephaly can occur either in association with the Miller-Dieker syndrome (MDS) or as an isolated finding, termed "isolated lissencephaly sequence" (ILS). About 90% of MDS patients have visible or submicroscopic deletions of 17p13.3. We therefore investigated the possibility that some ILS patients have smaller deletions in this chromosomal region. Forty-five ILS patients with gyral abnormalities ranging from complete agyria to mixed agyria/pachygyria and complete pachygyria were studied. RFLP analysis with five polymorphic loci in 17p13.3 was performed on all patients and their parents. Somatic cell hybrids were constructed on three patients, to confirm a deletion or to determine the boundaries of a deletion. In-situ hybridization using cosmid probes from within a newly defined lissencephaly critical region was performed on 31 patients as a further method of deletion detection. Six submicroscopic deletions were detected (13.3%). Three of the deletions among 45 ILS patients were detected by RFLP analysis, 4 deletions in 31 patients were detected by in situ hybridization, and one deletion was detected only by somatic cell hybrid studies (in situ hybridization was not performed). Overall, in situ hybridization proved to be the most rapid and sensitive method of deletion detection. The centromeric boundary of these deletions overlapped that of MDS patients, while the telomeric boundary for four ILS deletions was proximal to that of MDS and narrows the critical region for a lissencephaly locus.(ABSTRACT TRUNCATED AT 250 WORDS)
Base Sequence↗
Evidence for genetic heterogeneity in tuberous sclerosis: one locus on chromosome 9 and at least one locus elsewhere.
Linkage of tuberous sclerosis complex (TSC), an autosomal dominant disorder, to markers on chromosome 9 was reported first in 1987. This assignment was confirmed by an international collaborative study that suggested more than one locus may be responsible for the phenotype. We studied 14 multigenerational TSC families (13 previously unreported) with markers for nine loci in the linked region of chromosome 9q32-q34. Our results confirm the previous reports that the genetic locus in one-third to one-half of families maps to chromosome 9. Comparison of clinical findings in the chromosome 9-linked families with those in the chromosome 9-unlinked families reveals only a higher incidence of ungual fibromata in the chromosome 9-linked families.
Alleles↗
Epidermal nevus syndrome: a neurologic variant with hemimegalencephaly, gyral malformation, mental retardation, seizures, and facial hemihypertrophy.
The epidermal nevus syndrome (ENS) is a sporadic neurocutaneous disorder that consists of epidermal nevi and congenital anomalies involving the brain and other systems. From among over 60 patients with ENS presenting with neurologic manifestations, we identified 17 who had hemimegalencephaly based on pathologic or radiologic studies. Associated brain and neurologic abnormalities included gyral malformations in 12 of 12, mental retardation in 13 of 14, seizures in 16 of 17 (including 9 with infantile spasms), and contralateral hemiparesis in 7 of 12. All had ipsilateral epidermal nevi of the head, and several had ipsilateral facial hemihypertrophy. We concluded that these abnormalities comprise a recognizable neurologic variant of ENS that we believe represents the full expression of primary brain involvement. Several patients also had evidence of acquired brain lesions such as infarcts, atrophy, porencephaly, and calcifications, which are best explained by prior ischemia or hemorrhage. Given repeated observations of blood vessel anomalies in ENS patients, we hypothesize that underlying vascular dysplasia predisposes to these acquired lesions. The same cause may be invoked to explain the wide variety of neurologic symptoms reported in ENS patients without hemimegalencephaly. While the cause of ENS remains unknown, several observations suggest a somatic mutation.
Bone and Bones↗
Vascular abnormalities in epidermal nevus syndrome.
We report a patient with epidermal nevus syndrome and right hemispheric infarct and review 3 others with neurologic manifestations best explained by ischemia or hemorrhage. Each had a significant vascular abnormality such as occlusion or blood vessel dysplasia. None had hemimegalencephaly. We hypothesize that underlying vascular dysplasia is the cause of the neurologic lesions in these patients.
Adolescent↗
Clinical and molecular diagnosis of Miller-Dieker syndrome.
We report results of clinical, cytogenetic, and molecular studies in 27 patients with Miller-Dieker syndrome (MDS) from 25 families. All had severe type I lissencephaly with grossly normal cerebellum and a distinctive facial appearance consisting of prominent forehead, bitemporal hollowing, short nose with upturned nares, protuberant upper lip, thin vermilion border, and small jaw. Several other abnormalities, especially growth deficiency, were frequent but not constant. Chromosome analysis showed deletion of band 17p13 in 14 of 25 MDS probands. RFLP and somatic cell hybrid studies using probes from the 17p13.3 region including pYNZ22 (D17S5), pYNH37 (D17S28), and p144-D6 (D17S34) detected deletions in 19 of 25 probands tested including seven in whom chromosome analysis was normal. When the cytogenetic and molecular data are combined, deletions were detected in 21 of 25 probands. Parental origin of de novo deletions was determined in 11 patients. Paternal origin occurred in seven and maternal origin in four. Our demonstration of cytogenetic or molecular deletions in 21 of 25 MDS probands proves that deletion of a "critical region" comprising two or more genetic loci within band 17p13.3 is the cause of the MDS phenotype. We suspect that the remaining patients have smaller deletions involving the proposed critical region which are not detected with currently available probes.
Brain↗
Molecular analysis of the Smith-Magenis syndrome: a possible contiguous-gene syndrome associated with del(17)(p11.2).
We undertook clinical evaluation (32 cases) and molecular evaluation (31 cases) of unrelated patients affected with Smith-Magenis syndrome (SMS) associated with an interstitial deletion of band p11.2 of chromosome 17. Patients were evaluated both clinically and electrophysiologically for peripheral neuropathy, since markers showing close linkage to one form of Charcot-Marie-Tooth disease (CMT1A) map to this chromosomal region. The common clinical findings were broad flat midface with brachycephaly, broad nasal bridge, brachydactyly, speech delay, and hoarse, deep voice. Fifty-five percent of the patients showed clinical signs (e.g., decreased or absent deep tendon reflexes, pes planus or pes cavus, decreased sensitivity to pain, and decreased leg muscle mass) suggestive of peripheral neuropathy. However, unlike patients with CMT1A, these patients demonstrated normal nerve conduction velocities. Self-destructive behaviors, primarily onychotillomania and polyembolokoilamania, were observed in 67% of the patients, and significant symptoms of sleep disturbance were observed in 62%. The absence of REM sleep was demonstrated by polysomnography in two patients. Southern analysis indicated that most patients were deleted for five 17p11.2 markers--FG1 (D17S446), 1516 (D17S258), pYNM67-R5 (D17S29), pA10-41 (D17S71), and pS6.1-HB2 (D17S445)--thus defining a region which appears to be critical to SMS. The deletion was determined to be of paternal origin in nine patients and of maternal origin in six patients. The apparent random parental origin of deletion documented in 15 patients suggests that genomic imprinting does not play a role in the expression of the SMS clinical phenotype. Our findings suggest that SMS is likely a contiguous-gene deletion syndrome which comprises characteristic clinical features, developmental delay, clinical signs of peripheral neuropathy, abnormal sleep function, and specific behavioral anomalies.
Adolescent↗
Detection of deletions and cryptic translocations in Miller-Dieker syndrome by in situ hybridization.
Fluorescence in situ hybridization (FISH) using two cosmid probes (41A and P13) from the Miller-Dieker syndrome (MDS) critical region in 17p13.3 was performed in a blinded comparison of three MDS patients with submicroscopic deletions and in four normal relatives used as controls. The controls showed both chromosome 17 homologues labeled in 85%-95% of cells, while each patient showed only one homologue labeled in 75%-80% of cells. Two MDS patients with cryptic translocations were also studied. In one case, a patient and her mother had the same der(17) (p+), but the reciprocal product of the translocation could not be identified in the mother by G-banding (i.e., it was a "half-cryptic" translocation). FISH revealed a 3q;17p translocation. The other case involved a patient with apparently normal karyotype. Because a large molecular deletion was found, a translocation involving two G-negative telomeres (i.e., a "full-cryptic" translocation) was postulated. FISH studies on her father and normal brother showed an 8q;17p translocation. These studies demonstrate that in situ hybridization is an efficient method for deletion detection in Miller-Dieker syndrome. More important, parental studies by FISH on patients demonstrating molecular deletions and a normal karyotype may identify cryptic translocation events, which cannot be detected by other molecular genetic strategies. Similar in situ strategies for deletion detection can be developed for other microdeletion syndromes, such as Prader-Willi/Angelman syndrome or DiGeorge syndrome.
Abnormalities, Multiple↗
Rapid diagnosis of Miller-Dieker syndrome and isolated lissencephaly sequence by the polymerase chain reaction.
Probe YNZ22 (D17S5) is a highly polymorphic, variable number tandem repeat (VNTR) marker previously shown to be deleted in all patients with the Miller-Dieker syndrome (MDS) but not in patients with isolated lissencephaly sequence (ILS). Primers were constructed to the unique sequence flanking the polymorphic, repetitive region of YNZ22 for amplification by the polymerase chain reaction (PCR). Analysis of 118 normal individuals revealed 12 alleles (differing in copy number of a 70-bp repeat unit) ranging in size from 168 to 938 bp. A retrospective study of eight MDS and six ILS patients was consistent with Southern blot analysis in all cases except one. In the latter, a very large allele (12 copies of the repeat unit) in a patient and her mother failed to amplify on initial attempts, but was successfully amplified by reducing the concentration of genomic DNA used in the reaction. Prospective studies on two MDS and five ILS patients were successfully performed and confirmed in all cases by Southern blot analysis. From the total sample, restriction fragment length polymorphism (RFLP) analysis was fully informative in four of ten MDS patients and showed a deletion in all four cases. Nine of eleven ILS patients were heterozygous and therefore not deleted for YNZ22. Development of primers for additional polymorphic markers in the Miller-Dieker region will lead to a rapid PCR-based diagnostic approach for all MDS and ILS patients. PCR typing of YNZ22 will also facilitate use of this marker in other applications, including genetic linkage, paternity and forensic studies, and analysis of loss of heterozygosity in tumors.
Abnormalities, Multiple↗
Isolated lissencephaly: report of four patients from two unrelated families.
Lissencephaly is a brain malformation manifested by a smooth cerebral surface and caused by incomplete neuronal migration. Clinical sequellae include minor craniofacial changes (bitemporal hollowing, small jaw), severe mental retardation, and other neurological abnormalities. Patients with classical or type I lissencephaly and its sequellae but no other significant anomalies are classified as having isolated lissencephaly sequence. Possible causes of isolated lissencephaly sequence include ischemia or viral infection during the time of neuronal migration, microdeletion within the Miller-Dieker syndrome critical region in chromosome band 17p13.3, and Mendelian inheritance. The last is based on a report of a single family with three affected children in 1933. We report four patients with isolated lissencephaly sequence from two unrelated families who provide further support for autosomal (or possibly X-linked) recessive inheritance. In the first family, three brothers were affected. In the second, the parents are first cousins.
Brain↗