John J. Halperin

Whole-Genome Sequencing in a Patient with Charcot–Marie–Tooth Neuropathy

BACKGROUND Whole-genome sequencing may revolutionize medical diagnostics through rapid identification of alleles that cause disease. However, even in cases with simple patterns of inheritance and unambiguous diagnoses, the relationship between disease phenotypes and their corresponding genetic changes can be complicated. Comprehensive diagnostic assays must therefore identify all possible DNA changes in each haplotype and determine which are responsible for the underlying disorder. The high number of rare, heterogeneous mutations present in all humans and the paucity of known functional variants in more than 90% of annotated genes make this challenge particularly difficult. Thus, the identification of the molecular basis of a genetic disease by means of whole-genome sequencing has remained elusive. We therefore aimed to assess the usefulness of human whole-genome sequencing for genetic diagnosis in a patient with Charcot-Marie-Tooth disease. METHODS We identified a family with a recessive form of Charcot-Marie-Tooth disease for which the genetic basis had not been identified. We sequenced the whole genome of the proband, identified all potential functional variants in genes likely to be related to the disease, and genotyped these variants in the affected family members. RESULTS We identified and validated compound, heterozygous, causative alleles in SH3TC2 (the SH3 domain and tetratricopeptide repeats 2 gene), involving two mutations, in the proband and in family members affected by Charcot-Marie-Tooth disease. Separate subclinical phenotypes segregated independently with each of the two mutations; heterozygous mutations confer susceptibility to neuropathy, including the carpal tunnel syndrome. CONCLUSIONS As shown in this study of a family with Charcot-Marie-Tooth disease, whole-genome sequencing can identify clinically relevant variants and provide diagnostic information to inform the care of patients.

Linkage of a gene causing familial amyotrophic lateral sclerosis to chromosome 21 and evidence of genetic-locus heterogeneity

BACKGROUND Amyotrophic lateral sclerosis is a progressive neurologic disorder that commonly results in paralysis and death. Despite more than a century of research, no cause of, cure for, or means of preventing this disorder has been found. In a minority of cases, it is familial and inherited as an autosomal dominant trait with age-dependent penetrance. In contrast to the sporadic form of amyotrophic lateral sclerosis, the familial form provides the opportunity to use molecular genetic techniques to localize an inherited defect. Furthermore, such studies have the potential to discover the basic molecular defect causing motor-neuron degeneration. METHODS AND RESULTS We evaluated 23 families with familial amyotrophic lateral sclerosis for linkage of the gene causing this disease to four DNA markers on the long arm of chromosome 21. Multipoint linkage analyses demonstrated linkage between the gene and these markers. The maximum lod score--5.03--was obtained 10 centimorgans distal (telomeric) to the DNA marker D21S58. There was a significant probability (P less than 0.0001) of genetic-locus heterogeneity in the families. CONCLUSIONS The localization of a gene causing familial amyotrophic lateral sclerosis provides a means of isolating this gene and studying its function. Insight gained from understanding the function of this gene may be applicable to the design of rational therapy for both the familial and sporadic forms of the disease.

A study of the dynamics of retrograde transport and accumulation of horseradish peroxidase in injured neurons

The phenomenon of retrograde intraaxonal transport of extracellular markers introduced at the level of the axon terminal has been suggested as a possible mechanism of communication between the axon terminal and the neuron cell body. We tested the hypothesis that communication after axotomy might consist of a change in the rate of uptake or of transport of material by injured neurons. Small lesions were made with a needle in one retinal quadrant of chicks and immediately afterwards horseradish peroxidase (HRP) was injected into the vitreous body of the eye. The amount of HRP accumulated by some of the neurons of the isthmo-optic nucleus (ION) which project to the damaged area was clearly different from that of nearby cells which project to the non-damaged portions of the retina. The uninjured cells accumulated enzyme marker beginning at 3.5 h after injection. The injured neurons did not accumulate significant amounts of HRP until between 4 and 6 h after injection. Between 6.75 h and 18 h the injured cells in the ION accumulated greater amounts of HRP than cells in other regions, but by 24 h the cells of the ION in the region of injury contained distinctly less label. This pattern of enzyme accumulation was confirmed by counts of the number of HRP-positive granules within cells of chicks fixed 4, 11.75, 12.25, 27.6 and 72 h after injury. In another series of experiments, the axon terminals of the ION were first exposed to HRP, and 1 h later some of the axons were damaged with a needle. In these cases, there was no difference between the injured and control neurons in the time of first appearance of labeled cells in the ION within the first 4 h after injection of HRP. These findings suggest that injury initially results in a decrease in the uptake of the marker rather than a decrease in the rate of retrograde transport. The amount of marker found in the injured neurons later is greater than that found in the control neurons. This subsequent difference may represent an increase in the rate of uptake, transport, or both or a decrease in the rate of degradation of HRP within the cell body as a response to injury of the axon.

New chemotherapeutic approaches in the treatment of Lyme borreliosis.

1. It was demonstrated that while B. burgdorferi may be sensitive to relatively small concentrations of penicillin and ceftriaxone, the organism is killed slowly. This implies that, as in syphilis, prolonged blood levels of these drugs may be necessary in order to ensure cure. In contrast, the activity of tetracycline is more rapid in its action but is more dependent on drug concentration achieved. Unfortunately, the MIC and MBC for some strains are at or above the peak level achieved under optimal conditions. 2. Increasing the concentrations of penicillin or ceftriaxone above the MIC for the organism has little effect on the rate of killing. In contrast, the killing by tetracycline can be augmented by increasing concentrations of the drug. 3. Ceftriaxone is more active than penicillin, as measured by MIC, against the five strains of B. burgdorferi tested. 4. Ceftriaxone was efficacious in the treatment of Lyme borreliosis, which was recalcitrant to penicillin therapy. In a randomized trial comparing ceftriaxone to high-dose penicillin therapy, ceftriaxone was significantly more efficacious than penicillin in the treatment of the late complications of Lyme borreliosis.

Cranial computed tomography in Whipple's disease.

Cranial computed tomography (CT) in a 58-year-old man disclosed enhancing lesions in the medial right temporal lobe and the right pons. Biopsy of the sural nerve was positive for Whipples disease, and one of the temporal lobe lesions showed unprecedented histological findings. This case, to our knowledge, is unique in its demonstration of cranial CT findings in association with Whipples disease. It is suggested that a cranial CT scan with the use of intravenous contrast material should be performed in patients presenting with the signs or symptoms of Whipples disease.•51 year-old male with a one-month history of low back pain without radiating symptoms secondary to a work-related injury. •Symptoms compromise his ability to optimally perform regular work activities which include prolonged standing, walking, forward bending, and lifting. Core Strengthening and Lower Extremity Flexibility A Model for Physical Therapy Treatment of Acute Nonspecific Low Back Pain: A Case Report

Muscle Biopsy and the Clinical Course of Infantile Spinal Muscular Atrophy

Eight infants with severe early infantile spinal muscular atrophy diagnosed by clinical presentation and muscle biopsy were studied. The extent of alterations in muscle histology, histochemistry, and ultrastructure did not reflect the relative severity of the clinical presentation or the course of the illness. In seven biopsies, ultrastructural studies demonstrated empty sleeves of basal lamina projecting from the surface of small myofibers. We conclude that severe infantile spinal muscular atrophy often results in myofiber atrophy similar to that found in other motor neuron diseases, and it is not solely a hypotrophic process. Muscle biopsy findings are important because they help to establish the diagnosis, but they do not help predict the severity of disease among infants with this condition. (J Child Neurol 1991;6:324-328).