The natural history and genotype-phenotype correlations of TMPRSS3 hearing loss: an international, multi-center, cohort analysis

TMPRSS3-related hearing loss presents challenges in correlating genotypic variants with clinical phenotypes due to the small sample sizes of previous studies. We conducted a cross-sectional genomics study coupled with retrospective clinical phenotype analysis on 127 individuals. These individuals were from 16 academic medical centers across 6 countries. Key findings revealed 47 unique TMPRSS3 variants with significant differences in hearing thresholds between those with missense variants versus those with loss-of-function genotypes. The hearing loss progression rate for the DFNB8 subtype was 0.3 dB/year. Post-cochlear implantation, an average word recognition score of 76% was observed. Of the 51 individuals with two missense variants, 10 had DFNB10 with profound hearing loss. These 10 all had at least one of 4 TMPRSS3 variants predicted by computational modeling to be damaging to TMPRSS3 structure and function. To our knowledge, this is the largest study of TMPRSS3 genotype-phenotype correlations. We find significant differences in hearing thresholds, hearing loss progression, and age of presentation, by TMPRSS3 genotype and protein domain affected. Most individuals with TMPRSS3 variants perform well on speech recognition tests after cochlear implant, however increased age at implant is associated with worse outcomes. These findings provide insight for genetic counseling and the on-going design of novel therapeutic approaches.

Dispersed DNA variants underlie hearing loss in South Florida's minority population

BACKGROUND

We analyzed the genetic causes of sensorineural hearing loss in racial and ethnic minorities of South Florida by reviewing demographic, phenotypic, and genetic data on 136 patients presenting to the Hereditary Hearing Loss Clinic at the University of Miami. In our retrospective chart review, of these patients, half self-identified as Hispanic, and the self-identified racial distribution was 115 (86%) White, 15 (11%) Black, and 6 (4%) Asian. Our analysis helps to reduce the gap in understanding the prevalence, impact, and genetic factors related to hearing loss among diverse populations.

RESULTS

The causative gene variant or variants were identified in 54 (40%) patients, with no significant difference in the molecular diagnostic rate between Hispanics and Non-Hispanics. However, the total solve rate based on race was 40%, 47%, and 17% in Whites, Blacks, and Asians, respectively. In Non-Hispanic Whites, 16 different variants were identified in 13 genes, with GJB2 (32%), MYO7A (11%), and SLC26A4 (11%) being the most frequently implicated genes. In White Hispanics, 34 variants were identified in 20 genes, with GJB2 (22%), MYO7A (7%), and STRC-CATSPER2 (7%) being the most common. In the Non-Hispanic Black cohort, the gene distribution was evenly dispersed, with 11 variants occurring in 7 genes, and no variant was identified in 3 Hispanic Black probands. For the Asian cohort, only one gene variant was found out of 6 patients.

CONCLUSION

This study demonstrates that the diagnostic rate of genetic studies in hearing loss varies according to race in South Florida, with more heterogeneity in racial and ethnic minorities. Further studies to delineate deafness gene variants in underrepresented populations, such as African Americans/Blacks from Hispanic groups, are much needed to reduce racial and ethnic disparities in genetic diagnoses.

Preimplantation genetic testing for hereditary hearing loss in Chinese population

PURPOSE

To evaluate the clinical validity of preimplantation genetic testing (PGT) to prevent hereditary hearing loss (HL) in Chinese population.

METHODS

A PGT procedure combining multiple annealing and looping-based amplification cycles (MALBAC) and single-nucleotide polymorphisms (SNPs) linkage analyses with a single low-depth next-generation sequencing run was implemented. Forty-three couples carried pathogenic variants in autosomal recessive non-syndromic HL genes, GJB2 and SLC26A4, and four couples carried pathogenic variants in rare HL genes: KCNQ4, PTPN11, PAX3, and USH2A were enrolled.

RESULTS

Fifty-four in vitro fertilization (IVF) cycles were implemented, 340 blastocysts were cultured, and 303 (89.1%) of these received a definite diagnosis of a disease-causing variant testing, linkage analysis and chromosome screening. A clinical pregnancy of 38 implanted was achieved, and 34 babies were born with normal hearing. The live birth rate was 61.1%.

CONCLUSIONS AND RELEVANCE

In both the HL population and in hearing individuals at risk of giving birth to offspring with HL in China, there is a practical need for PGT. The whole genome amplification combined with NGS can simplify the PGT process, and the efficiency of PGT process can be improved by establishing a universal SNP bank of common disease-causing gene in particular regions and nationalities. This PGT procedure was demonstrated to be effective and lead to satisfactory clinical outcomes.

Identification of a genetic variant underlying familial cases of recurrent benign paroxysmal positional vertigo

Benign paroxysmal positional vertigo (BPPV) is the most common cause of vertigo in humans, yet the molecular etiology is currently unknown. Evidence suggests that genetic factors may play an important role in some cases of idiopathic BPPV, particularly in familial cases, but the responsible genetic variants have not been identified. In this study, we performed whole exome sequencing [including untranslated regions (UTRs)] of 12 families and Sanger sequencing of additional 30 families with recurrent BPPV in Caucasians from the United States (US) Midwest region, to identify the genetic variants responsible for heightened susceptibility to BPPV. Fifty non-BPPV families were included as controls. In silico and experimental analyses of candidate variants show that an insertion variant rs113784532 (frameshift causing truncation) in the neural cadherin gene PCDHGA10 (protocadherin-gamma A10) is an exceedingly strong candidate (p = 1.80x10-4 vs. sample controls; p = 5.85x10-19 vs. ExAC data; p = 4.9x10-3 vs. NHLBI exome data). The mutant protein forms large aggregates in BPPV samples even at young ages, and affected subjects carrying this variant have an earlier onset of the condition than those without [average 44.0±14.0 (n = 16) versus 54.4±16.1 (n = 36) years old, p = 0.054]. In both human and mouse inner ear tissues, PCDHGA10 is expressed in ganglia, hair cells and vestibular transitional epithelia. Fluorescent RNA in situ hybridization using mouse inner ear tissues shows that expression increases with age. In summary, our data show that a variant in the PCDHGA10 gene may be involved in causing or aggravating some familial cases of recurrent idiopathic BPPV.

A next-generation sequencing gene panel (MiamiOtoGenes) for comprehensive analysis of deafness genes

Extreme genetic heterogeneity along with remarkable variation in the distribution of causative variants across in different ethnicities makes single gene testing inefficient for hearing loss. We developed a custom capture/next-generation sequencing gene panel of 146 known deafness genes with a total target size of approximately 1 MB. The genes were identified by searching databases including Hereditary Hearing Loss Homepage, the Human Genome Mutation Database (HGMD), Online Mendelian Inheritance in Man (OMIM) and most recent peer-reviewed publications related to the genetics of deafness. The design covered all coding exons, UTRs and 25 bases of intronic flanking sequences for each exon. To validate our panel, we used 6 positive controls with variants in known deafness genes and 8 unsolved samples from individuals with hearing loss. Mean coverage of the targeted exons was 697X. On average, each sample had 99.8%, 96.2% and 92.7% of the targeted region coverage of 1X, 50X and 100X reads, respectively. Analysis detected all known variants in nuclear genes. These results prove the accuracy and reliability of the custom capture experiment.

Novel domain-specific POU3F4 mutations are associated with X-linked deafness: examples from different populations

Background

Mutations in the POU3F4 gene cause X-linked deafness type 3 (DFN3), which is characterized by inner ear anomalies.

Methods

Three Turkish, one Ecuadorian, and one Nigerian families were included based on either inner ear anomalies detected in probands or X-linked family histories. Exome sequencing and/or Sanger sequencing were performed in order to identify the causative DNA variants in these families.

Results

Four novel, c.707A>C (p.(Glu236Ala)), c.772delG (p.(Glu258ArgfsX30)), c.902C>T (p.(Pro301Leu)), c.987T>C (p.(Ile308Thr)), and one previously reported mutation c.346delG (p.(Ala116ProfsX26)) in POU3F4, were identified. All mutations identified are predicted to affect the POU-specific or POU homeo domains of the protein and co-segregated with deafness in all families.

Conclusions

Expanding the spectrum of POU3F4 mutations in different populations along with their associated phenotypes provides better understanding of their clinical importance and will be helpful in clinical evaluation and counseling of the affected individuals.

Electronic supplementary material

The online version of this article (doi:10.1186/s12881-015-0149-2) contains supplementary material, which is available to authorized users.

A missense mutation in DCDC2 causes human recessive deafness DFNB66, likely by interfering with sensory hair cell and supporting cell cilia length regulation

Hearing loss is the most common sensory deficit in humans. We show that a point mutation in DCDC2 (DCDC2a), a member of doublecortin domain-containing protein superfamily, causes non-syndromic recessive deafness DFNB66 in a Tunisian family. Using immunofluorescence on rat inner ear neuroepithelia, DCDC2a was found to localize to the kinocilia of sensory hair cells and the primary cilia of nonsensory supporting cells. DCDC2a fluorescence is distributed along the length of the kinocilium with increased density toward the tip. DCDC2a-GFP overexpression in non-polarized COS7 cells induces the formation of long microtubule-based cytosolic cables suggesting a role in microtubule formation and stabilization. Deafness mutant DCDC2a expression in hair cells and supporting cells causes cilium structural defects, such as cilium branching, and up to a 3-fold increase in length ratios. In zebrafish, the ortholog dcdc2b was found to be essential for hair cell development, survival and function. Our results reveal DCDC2a to be a deafness gene and a player in hair cell kinocilia and supporting cell primary cilia length regulation likely via its role in microtubule formation and stabilization.

Identification of copy number variants through whole-exome sequencing in autosomal recessive nonsyndromic hearing loss

Genetic variants account for more than half of the cases with congenital or prelingual onset hearing loss. Autosomal recessive nonsyndromic hearing loss (ARNSHL) is the most common subgroup. Whole-exome sequencing (WES) has been shown to be effective detecting deafness-causing single-nucleotide variants (SNVs) and insertion/deletions (INDELs). After analyzing the WES data for causative SNVs or INDELs involving previously reported deafness genes in 78 families with ARNSHL, we searched for copy number variants (CNVs) through two different tools in 24 families that remained unresolved. We detected large homozygous deletions in STRC and OTOA in single families. Thus, causative CNVs in known deafness genes explain 2 out of 78 (2.6%) families in our sample set. We conclude that CNVs can be reliably detected through WES and should be the part of pipelines used to clarify genetic basis of hearing loss.

De novo ACTG2 mutations cause congenital distended bladder, microcolon, and intestinal hypoperistalsis

Megacystis-microcolon-intestinal hypoperistalsis syndrome (MMIHS) is characterized by prenatal-onset distended urinary bladder with functional intestinal obstruction, requiring extensive surgical intervention for survival. While it is believed to be an autosomal recessive disorder, most cases are sporadic. Through whole-exome sequencing in a child with MMIHS, we identified a de novo mutation, p.R178L, in the gene encoding the smooth muscle gamma-2 actin, ACTG2. We subsequently detected another de novo ACTG2 mutation, p.R178C, in an additional child with MMIHS. Actg2 transcripts were primarily found in murine urinary bladder and intestinal tissues. Structural analysis and functional experiments suggested that both ACTG2 mutants interfere with proper polymerization of ACTG2 into thin filaments, leading to impaired contractility of the smooth muscle. In conclusion, our study suggests a pathogenic mechanism for MMIHS by identifying causative ACTG2 mutations.

Implementing Genomic Medicine in Care of Patients with Impaired Hearing

Objectives:

The Miami Otogenetic Program has provided a unique platform to carry out translational research on delivering genetic services to deafness patient care. Using target-enrichment/NGS, we will 1) determine the overall frequencies of different forms of genetic deafness, 2) identify new genes for ARSNHL and ADNSHL, and 3) create a Genomic Deafness Database (GDD) and Personalized Sequence Profile (PSP) for the clinical care of deaf patients.

Methods:

We collected a unique cohort of multiplex families derived from three unique sources from the U.S., China, and Turkey, suitable for determination of molecular epidemiology of hereditary deafness and for new gene identification using “target-enrichment,” methods and next generation sequencing (NGS). Our interdisciplinary and collaborative team will conduct outcomes evaluation of genetic service on deaf patient care in our diverse populations.

Results:

The infrastructure of our multidisciplinary otogenetics team is presented along with our use of testing algorithms when evaluating patients with sensorineural hearing loss (SNHL). A total of 60% of small multiplex families are identified to have mutations in the known deafness genes in a pilot study and the remaining 40% have mutations in other yet-unidentified deafness-causing genes. We have identified several new genes for SNHL.

Conclusions:

The combined target-enrichment/NGS is a powerful tool in the identification of new deafness genes in small multiplex families and large multi-generational families. The multidisciplinary team approach is an effective way to bring the sequencing data to clinical practice for the clinical diagnosis and management of deaf and hard-of-hearing families.

Abstract 14: Fine Mapping Study Revealed Novel Candidate Genes for Carotid Intima-Media Thickness in Dominicans

Background: Carotid intima-media thickness (CIMT) is a subclinical measure for atherosclerosis, the major underlying cause for stroke and other cardiovascular events. Previously, we have mapped quantitative trait loci (QTLs) for CIMT to chromosomes 7p (MLOD=3.1) and 14q (MLOD=2.3) in 100 extended Dominican Republican (DR) families.

Methods and Results: To identify the genetic variations accounting for CIMT variability at those QTLs, we surveyed the one-LOD-unit-down linkage regions using >2,000 tagging single nucleotide polymorphisms (SNPs). Family-based association tests were performed in the 100 DR families (N=1372) used in the original linkage study, adjusting for significant covariants. Promising SNPs were further examined in the population-based NOMAS subcohort comprised of DR subjects only (N=553). Evidence for association (P<0.001) was found in multiple genes ( ANLN , AOAH, FOXN3, CCDC88C, PRiMA1, and an intergenic SNP rs1667498 near FLRT2) with the strongest association at PRiMA1 (P=0.00007, which remained significant after adjusting for multiple testing). The association at these genes, except for PRiMA1, was driven by families with evidence for linkage (53 and 51 families for the 7p and 14q QTL, respectively; P= 0.00004∼0.00092 and 0.13∼0.80 in families with and without evidence for linkage, respectively), suggesting that these genes might collectively account for the QTLs delimited in our family data set. On the other hand, the association at PRiMA1 is significant in both family subsets (P=0.002 and 0.019 in families with and without evidence for linkage, respectively). The association at PRiMA1, but not at other genes, was replicated in the NOMAS DR subcohort (P=0.047), supporting a robust association at PRiMA1 .

Conclusions: We identified several candidate genes for CIMT in Dominican Republicans. Some of the genes manifest genetic effects within a specific subset of families and others can be generalized in additional samples. Future studies are needed to further elucidate the contribution of these genes to atherosclerosis.

Mutations in ANKRD11 cause KBG syndrome, characterized by intellectual disability, skeletal malformations, and macrodontia

KBG syndrome is characterized by intellectual disability associated with macrodontia of the upper central incisors as well as distinct craniofacial findings, short stature, and skeletal anomalies. Although believed to be genetic in origin, the specific underlying defect is unknown. Through whole-exome sequencing, we identified deleterious heterozygous mutations in ANKRD11 encoding ankyrin repeat domain 11, also known as ankyrin repeat-containing cofactor 1. A splice-site mutation, c.7570-1G>C (p.Glu2524_Lys2525del), cosegregated with the disease in a family with three affected members, whereas in a simplex case a de novo truncating mutation, c.2305delT (p.Ser769GlnfsX8), was detected. Sanger sequencing revealed additional de novo truncating ANKRD11 mutations in three other simplex cases. ANKRD11 is known to interact with nuclear receptor complexes to modify transcriptional activation. We demonstrated that ANKRD11 localizes mainly to the nuclei of neurons and accumulates in discrete inclusions when neurons are depolarized, suggesting that it plays a role in neural plasticity. Our results demonstrate that mutations in ANKRD11 cause KBG syndrome and outline a fundamental role of ANKRD11 in craniofacial, dental, skeletal, and central nervous system development and function.

Whole-exome sequencing links a variant in DHDDS to retinitis pigmentosa

Increasingly, mutations in genes causing Mendelian disease will be supported by individual and small families only; however, exome sequencing studies have thus far focused on syndromic phenotypes characterized by low locus heterogeneity. In contrast, retinitis pigmentosa (RP) is caused by >50 known genes, which still explain only half of the clinical cases. In a single, one-generation, nonsyndromic RP family, we have identified a gene, dehydrodolichol diphosphate synthase (DHDDS), demonstrating the power of combining whole-exome sequencing with rapid in vivo studies. DHDDS is a highly conserved essential enzyme for dolichol synthesis, permitting global N-linked glycosylation. Zebrafish studies showed virtually identical photoreceptor defects as observed with N-linked glycosylation-interfering mutations in the light-sensing protein rhodopsin. The identified Lys42Glu variant likely arose from an ancestral founder, because eight of the nine identified alleles in 27,174 control chromosomes were of confirmed Ashkenazi Jewish ethnicity. These findings demonstrate the power of exome sequencing linked to functional studies when faced with challenging study designs and, importantly, link RP to the pathways of N-linked glycosylation, which promise new avenues for therapeutic interventions.

Canine RPGRIP1 mutation establishes cone–rod dystrophy in miniature longhaired dachshunds as a homologue of human Leber congenital amaurosis

Cone-rod dystrophy 1 (cord1) is a recessive condition that occurs naturally in miniature longhaired dachshunds (MLHDs). We mapped the cord1 locus to a region of canine chromosome CFA15 that is syntenic with a region of human chromosome 14 (HSA14q11.2) containing the retinitis pigmentosa GTPase regulator-interacting protein 1 (RPGRIP1) gene. Mutations in RPGRIP1 have been shown to cause Leber congenital amaurosis, a group of retinal dystrophies that represent the most common genetic causes of congenital visual impairment in infants and children. Using the newly available canine genome sequence we sequenced RPGRIP1 in affected and carrier MLHDs and identified a 44-nucleotide insertion in exon 2 that alters the reading frame and introduces a premature stop codon. All affected and carrier dogs within an extended inbred pedigree were homozygous and heterozygous, respectively, for the mutation. We conclude the mutation is responsible for cord1 and demonstrate that this canine disease is a valuable model for exploring disease mechanisms and potential therapies for human Leber congenital amaurosis.

Treatment of upper motoneuron plantarflexion contractures by using an adjustable ankle-foot orthosis

OBJECTIVE

To assess the effectiveness of an adjustable ankle-foot orthosis in the treatment of plantarflexion contractures after central nervous system injury or disease.

DESIGN

Prospective, nonrandomized, interventional trial.

SETTING

University medical center's acute inpatient rehabilitation hospital.

PARTICIPANTS

Nine ankles with plantarflexion contractures that could not be passively reduced to less than neutral position occurring in 6 patients with stroke or other acquired brain injury.

INTERVENTION

To assure differentiation between spastic deformity and true contracture, patients received a 2% lidocaine block of the posterior tibial nerve. The adjustable ankle-foot orthosis was then applied on the affected ankle for 23 hours per day for 14 days. Adjustments to increase dorsiflexion passive range of motion (PROM) ranged from 0 degrees to 4.5 degrees and were attempted every 48 to 72 hours.

MAIN OUTCOME MEASURES

Dorsiflexion PROM at the ankle with the knee extended.

RESULTS

Increased PROM (average, 20.1 degrees; range, 6 degrees--36 degrees ) was statistically significant (p =.0078). Complications related to pressure with erythema or blister formation associated with pain occurred in 44% of treated ankles at some time during the 2-week trial period.

CONCLUSION

Plantarflexion contractures can be significantly reduced by using the adjustable ankle-foot orthosis with minimal complications.

An application of upper-extremity constraint-induced movement therapy in a patient with subacute stroke

BACKGROUND AND PURPOSE

The purpose of this case report is to demonstrate the application of constraint-induced movement therapy with an individual with upper-extremity hemiparesis within 4 months after sustaining a cerebrovascular accident (stroke). Such patients often fail to develop full potential use of their affected upper extremity, perhaps due to a "learned nonuse phenomenon."

CASE DESCRIPTION

The patient was a 61-year-old woman with right-sided hemiparesis resulting from an ischemic lacunar infarct in the posterior limb of the left internal capsule. The patient's less-involved hand was constrained in a mitten so that she could not use the hand during waking hours, except for bathing and toileting. On each weekday of the 14-day intervention period, the patient spent 6 hours being supervised while performing tasks using the paretic upper extremity. Pretreatment, posttreatment, and 3-month follow-up outcome measures included the Wolf Motor Function Test and the Motor Activity Log (MAL).

OUTCOMES

For the Wolf Motor Function Test, both the mean and median times to complete 16 tasks improved from pretreatment to posttreatment and from posttreatment to follow-up. Results of the MAL indicated an improved self-report of both "how well" and "how much" the patient used her affected limb in 30 specified daily tasks. These improvements persisted to the follow-up.

DISCUSSION

Two weeks of constraining the unaffected limb, coupled with practice of functional movements of the impaired limb, may be an effective method for restoring motor function within a few months after cerebral insult. Encouraging improvements such as these strongly suggest the need for a group design that would explore this type of intervention in more detail.

Correlation between Waardenburg syndrome phenotype and genotype in a population of individuals with identified PAX3 mutations

Waardenburg syndrome (WS) type 1 is an autosomal dominant disorder characterized by sensorineural hearing loss, pigmentary abnormalities of the eye, hair, and skin, and dystopia canthorum. The phenotype is variable and affected individuals may exhibit only one or a combination of several of the associated features. To assess the relationship between phenotype and gene defect, clinical and genotype data on 48 families (271 WS individuals) collected by members of the Waardenburg Consortium were pooled. Forty-two unique mutations in the PAX3 gene, previously identified in these families, were grouped in five mutation categories: amino acid (AA) substitution in the paired domain, AA substitution in the homeodomain, deletion of the Ser-Thr-Pro-rich region, deletion of the homeodomain and the Ser-Thr-Pro-rich region, and deletion of the entire gene. These mutation classes are based on the structure of the PAX3 gene and were chosen to group mutations predicted to have similar defects in the gene product. Association between mutation class and the presence of hearing loss, eye pigment abnormality, skin hypopigmentation, or white forelock was evaluated using generalized estimating equations, which allowed for incorporation of a correlation structure that accounts for potential similarity among members of the same family. Odds for the presence of eye pigment abnormality, white forelock, and skin hypopigmentation were 2, 8, and 5 times greater, respectively, for individuals with deletions of the homeodomain and the Pro-Ser-Thr-rich region compared to individuals with an AA substitution in the homeodomain. Odds ratios that differ significantly from 1.0 for these traits may indicate that the gene products resulting from different classes of mutations act differently in the expression of WS. Although a suggestive association was detected for hearing loss with an odds ratio of 2.6 for AA substitution in the paired domain compared with AA substitution in the homeodomain, this odds ratio did not differ significantly from 1.0.

Cosegregation of familial intestinal pseudoobstruction and presence of digital arches in a large multigenerational pedigree

Previous studies have suggested a relationship between the presence of digital arches and the occurrence of early-onset chronic intestinal pseudoobstruction (CIP). We recently had under our care a patient who died of complications from neuropathic familial CIP (FCIP) and who had family members with symptoms and radiographic findings consistent with FCIP. Our aim was to determine if there is a relationship between FCIP and digital arches using members of this patient's family tree. Questionnaires, telephone follow-up, and clinical and radiographic evidence were all utilized to determine whether a diagnosis of CIP could be made for the family members of this deceased FCIP patient. Fingerprints were sought for all study subjects. Eight of the 26 study subjects who were fingerprinted had clinically diagnosed FCIP and four of these eight had radiographic confirmation. All eight were positive for one or more arches (sensitivity = 100%). Only one of the 18 subjects without a diagnosis of FCIP who were fingerprinted had arches (specifically 94%). The likelihood of linkage between the presence of digital arches and FCIP in our study family was significant by genetic linkage analysis criteria. These results show a significant correlation between FCIP and digital arches (P < 0.0001). Whether this relationship is a causal one, ie, the gene responsible for digital arches is also responsible for FCIP, or is the result of linkage between the genes for FCIP and digital arches remains unclear.

Overcoming limitations in elbow movement in the presence of antagonist hyperactivity

BACKGROUND AND PURPOSE

A traditional perspective on rehabilitation of patients with abnormal muscular hyperactivity presumes that relaxation should be facilitated prior to recruitment of antagonists, if effective movement about a joint is to occur. The purpose of the study was to determine the effect of training weak triceps brachii muscles, with hyperactivity present in the opposing biceps brachii muscles, on elbow function in individuals at least 1 year poststroke.

SUBJECTS

Sixteen patients with chronic stroke were randomly assigned to receive electromyographic biofeedback to retrain the triceps muscle (n = 8) or to receive conventional movement training (n = 8).

METHODS

Both groups participated in 5 baseline and 10 training sessions involving tasks requiring elbow extension. Preintervention and postintervention measurements included elbow extension range of motion, triceps and biceps muscle electromyographic activity during performance of elbow extension, resisted elbow extension, and a reaching task.

RESULTS

Two-sample t-test results of between-group comparisons for each variable were not significant. One-sample t-test results of within-group comparisons showed significant increases in triceps muscle mean electromyographic activity during two of the three tasks for the feedback group, but not for the nonfeedback group. Passive and active range of motion in both groups increased significantly, although biceps muscle co-contraction persisted.

CONCLUSION AND DISCUSSION

These results suggest that functional improvements at the elbow may have been due to biomechanical (peripheral) rather than neuromuscular (central) changes about the joint. Furthermore, these preliminary data indicate that patients with stroke may be trained to increase movement without first being trained to specifically inhibit hyperactivity in muscles.

PRP38 encodes a yeast protein required for pre-mRNA splicing and maintenance of stable U6 small nuclear RNA levels

An essential pre-mRNA splicing factor, the product of the PRP38 gene, has been genetically identified in a screen of temperature-sensitive mutants of Saccharomyces cerevisiae. Shifting temperature-sensitive prp38 cultures from 23 to 37 degrees C prevents the first cleavage-ligation event in the excision of introns from mRNA precursors. In vitro splicing inactivation and complementation studies suggest that the PRP38-encoded factor functions, at least in part, after stable splicing complex formation. The PRP38 locus contains a 726-bp open reading frame coding for an acidic 28-kDa polypeptide (PRP38). While PRP38 lacks obvious structural similarity to previously defined splicing factors, heat inactivation of PRP38, PRP19, or any of the known U6 (or U4/U6) small nuclear ribonucleoprotein-associating proteins (i.e., PRP3, PRP4, PRP6, and PRP24) leads to a common, unexpected consequence: intracellular U6 small nuclear RNA (snRNA) levels decrease as splicing activity is lost. Curiously, U4 snRNA, normally extensively base paired with U6 snRNA, persists in the virtual absence of U6 snRNA.