Congenital mirror movements: Phenotypes associated with DCC and RAD51 mutations

Aberrant connectivity of the lateralized readiness system in non-syndromic congenital mirror movements

OBJECTIVES

Non-syndromic CMM has a complex phenotype. Abnormal corpus callosum and corticospinal tract processes are suggested mechanisms of the mirror movements. To further explore behavioural and neural phenotype(s) the present study tests the hypothesis that the response readiness network comprising supplementary motor area (SMA) and connections with motor cortex (M1) functions abnormally in CMM.

METHODS

Twelve participants with (non-syndromic) CMM and a control group (n = 28) were tested on a probabilistic Go-NoGo task while electroencephalography (EEG) was recorded to assess possible group differences in lateralized readiness of voluntary hand movements together with measures of SMA-M1 functional connectivity.

RESULTS

The CMM group demonstrated delayed lateralized readiness and stronger functional connectivity between left-brain SMA-M1 regions. Connectivity strength was correlated with measures of behavioural performance but not with extent of mirroring.

CONCLUSIONS

Abnormalities in brain processes upstream of movement output likely reflect neurocompensation as a result of lifelong experience with mirroring in CMM.

SIGNIFICANCE

These findings extend the known neural abnormalities in CMM to include brain networks upstream from those involved in motor output and raise the question of whether neurocompensatory plasticity might be involved.

Insights from the neural guidance factor Netrin-1 into neurodegeneration and other diseases

Netrin-1 was initially discovered as a neuronal growth cue for axonal guidance, and its functions have later been identified in inflammation, tumorigenesis, neurodegeneration, and other disorders. We have recently found its alterations in the brains with Alzheimer's disease, which might provide important clues to the mechanisms of some unique pathologies. To provide better understanding of this promising molecule, we here summarize research progresses in genetics, pathology, biochemistry, cell biology and other studies of Netrin-1 about its mechanistic roles and biomarker potentials with an emphasis on clinical neurodegenerative disorders in order to expand understanding of this promising molecular player in human diseases.

Paroxysmal Dystonic Posturing Mimicking Nocturnal Leg Cramps as a Presenting Sign in an Infant with DCC Mutation, Callosal Agenesis and Mirror Movements

Background/Objectives: Pathogenic variants in the deleted in colorectal cancer gene (DCC), encoding the Netrin-1 receptor, may lead to mirror movements (MMs) associated with agenesis/dysgenesis of the corpus callosum (ACC) and cognitive and/or neuropsychiatric issues. The clinical phenotype is related to the biological function of DCC in the corpus callosum and corticospinal tract development as Netrin-1 is implicated in the guidance of developing axons toward the midline. We report on a child with a novel inherited, monoallelic, pathogenic variant in the DCC gene. Methods: Standardized measures and clinical scales were used to assess psychomotor development, communication and social skills, emotional and behavioural difficulties. MMs were measured via the Woods and Teuber classification. Exome sequencing was performed on affected and healthy family members. Results: The patient's clinical presentation during infancy consisted of paroxysmal dystonic posturing when asleep, mimicking nocturnal leg cramps. A brain magnetic resonance imaging (MRI) showed complete ACC. He developed typical upper limb MMs during childhood and a progressively evolving neuro-phenotype with global development delay and behavioural problems. We found an intrafamilial clinical variability associated with DCC mutations: the proband's father and uncle shared the same DCC variant, with a milder clinical phenotype. The atypical early clinical presentation of the present patient expands the clinical spectrum associated with DCC variants, especially those in the paediatric age. Conclusions: This study underlines the importance of in-depth genetic investigations in young children with ACC and highlights the need for further detailed analyses of early motor symptoms in infants with DCC mutations.

Defining the Genetic Landscape of Congenital Mirror Movements in 80 Affected Individuals

BACKGROUND

Congenital mirror movements (CMM) is a rare neurodevelopmental disorder characterized by involuntary movements from one side of the body that mirror voluntary movements on the opposite side. To date, five genes have been associated with CMM, namely DCC, RAD51, NTN1, ARHGEF7, and DNAL4.

OBJECTIVE

The aim of this study is to characterize the genetic landscape of CMM in a large group of 80 affected individuals.

METHODS

We screened 80 individuals with CMM from 43 families for pathogenic variants in CMM genes. In large CMM families, we tested for presence of pathogenic variants in multiple affected and unaffected individuals. In addition, we evaluated the impact of three missense DCC variants on binding between DCC and Netrin-1 in vitro.

RESULTS

Causal pathogenic/likely pathogenic variants were found in 35% of probands overall, and 70% with familial CMM. The most common causal gene was DCC, responsible for 28% of CMM probands and 80% of solved cases. RAD51, NTN1, and ARHGEF7 were rare causes of CMM, responsible for 2% each. Penetrance of CMM in DCC pathogenic variant carriers was 68% and higher in males than females (74% vs. 54%). The three tested missense variants (p.Ile164Thr; p.Asn176Ser; and p.Arg1343His) bind Netrin-1 similarly to wild type DCC.

CONCLUSIONS

A genetic etiology can be identified in one third of CMM individuals, with DCC being the most common gene involved. Two thirds of CMM individuals were unsolved, highlighting that CMM is genetically heterogeneous and other CMM genes are yet to be discovered. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Congenital mirror movements are associated with defective polymerisation of RAD51

BACKGROUND

Mirror movements are involuntary movements of one hand that mirror intentional movements of the other hand. Congenital mirror movements (CMM) is a rare genetic disorder with autosomal dominant inheritance, in which mirror movements are the main neurological manifestation. CMM is associated with an abnormal decussation of the corticospinal tract, a major motor tract for voluntary movements. RAD51 is known to play a key role in homologous recombination with a critical function in DNA repair. While RAD51 haploinsufficiency was first proposed to explain CMM, other mechanisms could be involved.

METHODS

We performed Sanger sequencing of RAD51 in five newly identified CMM families to identify new pathogenic variants. We further investigated the expression of wild-type and mutant RAD51 in the patients' lymphoblasts at mRNA and protein levels. We then characterised the functions of RAD51 altered by non-truncating variants using biochemical approaches.

RESULTS

The level of wild-type RAD51 protein was lower in the cells of all patients with CMM compared with their non-carrier relatives. The reduction was less pronounced in asymptomatic carriers. In vitro, mutant RAD51 proteins showed loss-of-function for polymerisation, DNA binding and strand exchange activity.

CONCLUSION

Our study demonstrates that RAD51 haploinsufficiency, including loss-of-function of non-truncating variants, results in CMM. The incomplete penetrance likely results from post-transcriptional compensation. Changes in RAD51 levels and/or polymerisation properties could influence guidance of the corticospinal axons during development. Our findings open up new perspectives to understand the role of RAD51 in neurodevelopment.

Noncanonical Roles of RAD51

Homologous recombination (HR), an evolutionary conserved pathway, plays a paramount role(s) in genome plasticity. The pivotal HR step is the strand invasion/exchange of double-stranded DNA by a homologous single-stranded DNA (ssDNA) covered by RAD51. Thus, RAD51 plays a prime role in HR through this canonical catalytic strand invasion/exchange activity. The mutations in many HR genes cause oncogenesis. Surprisingly, despite its central role in HR, the invalidation of RAD51 is not classified as being cancer prone, constituting the "RAD51 paradox". This suggests that RAD51 exercises other noncanonical roles that are independent of its catalytic strand invasion/exchange function. For example, the binding of RAD51 on ssDNA prevents nonconservative mutagenic DNA repair, which is independent of its strand exchange activity but relies on its ssDNA occupancy. At the arrested replication forks, RAD51 plays several noncanonical roles in the formation, protection, and management of fork reversal, allowing for the resumption of replication. RAD51 also exhibits noncanonical roles in RNA-mediated processes. Finally, RAD51 pathogenic variants have been described in the congenital mirror movement syndrome, revealing an unexpected role in brain development. In this review, we present and discuss the different noncanonical roles of RAD51, whose presence does not automatically result in an HR event, revealing the multiple faces of this prominent actor in genomic plasticity.

Mirror movements and callosal dysgenesis in a family with a DCC mutation: Neuropsychological and neuroimaging outcomes

Corpus callosum dysgenesis is a congenital abnormality whereby the corpus callosum fails to develop normally, and has been associated with a range of neuropsychological outcomes. One specific finding in some individuals with corpus callosum dysgenesis is "congenital mirror movement disorder", which is the presence of involuntary movements on one side of the body that mimic voluntary movements of the other side. Mirror movements have also been associated with mutations in the deleted in colorectal carcinoma (DCC) gene. The current study aims to comprehensively document the neuropsychological outcomes and neuroanatomical mapping of a family (a mother, daughter and son) with known DCC mutations. All three family members experience mirror movements, and the son additionally has partial agenesis of the corpus callosum (pACC). All family members underwent extensive neuropsychological testing, spanning general intellectual functioning, memory, language, literacy, numeracy, psychomotor speed, visuospatial perception, praxis and motor functioning, executive functioning, attention, verbal/nonverbal fluency, and social cognition. The mother and daughter had impaired memory for faces, and reduced spontaneous speech, and the daughter demonstrated scattered impairments in attention and executive functioning, but their neuropsychological abilities were largely within normal limits. By contrast, the son showed areas of significant impairment across multiple domains including reduced psychomotor speed, fine motor dexterity and general intellectual functioning, and he was profoundly impaired across areas of executive functioning and attention. Reductions in his verbal/non-verbal fluency, with relatively intact core language, resembled dynamic frontal aphasia. His relative strengths included aspects of memory and he demonstrated largely sound theory of mind. Neuroimaging revealed an asymmetric sigmoid bundle in the son, connecting, via the callosal remnant, the left frontal cortex with contralateral parieto-occipital cortex. Overall, this study documents a range of neuropsychological and neuroanatomical outcomes within one family with DCC mutations and mirror movements, including one with more severe consequences and pACC.

Congenital Mirror Movements Associated With Brain Malformations

BACKGROUND

Congenital mirror movements are involuntary movements of a side of the body imitating intentional movements on the opposite side, appearing in early childhood and persisting beyond 7 years of age. Congenital mirror movements are usually idiopathic but have been reported in association with various brain malformations.

METHODS

We describe clinical, genetic, and radiologic features in 9 individuals from 5 families manifesting congenital mirror movements.

RESULTS

The brain malformations associated with congenital mirror movements were: dysplastic corpus callosum in father and daughter with a heterozygous p.Met1* mutation in DCC; hypoplastic corpus callosum, dysgyria, and malformed vermis in a mother and son with a heterozygous p.Thr312Met mutation in TUBB3; dysplastic corpus callosum, dysgyria, abnormal vermis, and asymmetric ventricles in a father and 2 daughters with a heterozygous p.Arg121Trp mutation in TUBB; hypoplastic corpus callosum, dysgyria, malformed basal ganglia and abnormal vermis in a patient with a heterozygous p.Glu155Asp mutation in TUBA1A; hydrocephalus, hypoplastic corpus callosum, polymicrogyria, and cerebellar cysts in a patient with a homozygous p.Pro312Leu mutation in POMGNT1.

CONCLUSION

DCC, TUBB3, TUBB, TUBA1A, POMGNT1 cause abnormal axonal guidance via different mechanisms and result in congenital mirror movements associated with brain malformations.

Heterozygous variants in DCC: Beyond congenital mirror movements

Objective

To perform a comprehensive characterization of a cohort of patients with congenital mirror movements (CMMs) in Sweden.

Methods

Clinical examination with the Woods and Teuber scale for mirror movements (MMs), neuroimaging, navigated transcranial magnetic stimulation (nTMS), and massive parallel sequencing (MPS) were applied.

Results

The cohort is ethnically diverse and includes a total of 7 patients distributed in 2 families and 2 sporadic cases. The degree of MMs was variable in this cohort. MPS revealed 2 novel heterozygous frameshift variants in DCC netrin 1 receptor (DCC). Two siblings harboring the pathogenic variant in c.1466_1476del display a complex syndrome featuring MMs and in 1 case receptive-expressive language disorder, chorea, epilepsy, and agenesis of the corpus callosum. The second DCC variant, c.1729delG, was associated with a typical benign CMM phenotype. No variants in DCC, NTN1, RAD51, or DNAL4 were found for the 2 sporadic CMM cases. However, one of these sporadic cases had concomitant high-risk myelodysplastic syndrome and a homozygous variant in ERCC excision repair like 2 (ERCC6L2). Reorganized corticospinal projection patterns to upper extremities were demonstrated with nTMS.

Conclusions

The presence of chorea expands the clinical spectrum of syndromes associated with variants in DCC. Biallelic pathogenic variants in ERCC6L2 cause bone marrow failure, but a potential association with CMM remains to be studied in larger cohorts.

A novel heterozygous loss-of-function DCC Netrin 1 receptor variant in prenatal agenesis of corpus callosum and review of the literature

Agenesis of the corpus callosum (ACC) is a common prenatally-detected brain anomaly. Recently, an association between mutations in the DCC Netrin 1 receptor (DCC) gene and ACC, with or without mirror movements, has been demonstrated. In this manuscript, we present a family with a novel heterozygous frameshift mutation in DCC, review the available literature, and discuss the challenges involved in the genetic counseling for recently discovered disorders with paucity of medical information. We performed whole exome sequencing in a healthy nonconsanguineous couple that underwent two pregnancy terminations due to prenatal diagnosis of ACC. A heterozygous variant c.2774dupA (p.Asn925Lysfs*17) in the DCC gene was demonstrated in fetal and paternal DNA samples, as well as in a healthy 4-year-old offspring. When directly questioned, both father and child reported having mirror movements not affecting quality of life. Segregation analysis demonstrated the variant in three paternal siblings, two of them having mirror movements. Brain imaging revealed normal corpus callosum. Summary of literature data describing heterozygous loss-of-function variants in DCC (n = 61) revealed 63.9% penetrance for mirror movements, 9.8% for ACC, and 5% for both. No significant neurodevelopmental abnormalities were reported among the seven published patients with DCC loss-of-function variants and ACC. Prenatal diagnosis of ACC should prompt a specific anamnesis regarding any neurological disorder, as well as intentional physical examination of both parents aimed to detect mirror movements. In suspicious cases, detection of DCC pathogenic variants might markedly improve the predicted prognosis, alleviate the parental anxiety, and possibly prevent pregnancy termination.

Neural function in DCC mutation carriers with and without mirror movements

Objective

Recently identified mutations of the axon guidance molecule receptor gene, DCC, present an opportunity to investigate, in living human brain, mechanisms affecting neural connectivity and the basis of mirror movements, involuntary contralateral responses that mirror voluntary unilateral actions. We hypothesized that haploinsufficient DCC^+/− mutation carriers with mirror movements would exhibit decreased DCC mRNA expression, a functional ipsilateral corticospinal tract, greater “mirroring” motor representations, and reduced interhemispheric inhibition. DCC^+/− mutation carriers without mirror movements might exhibit some of these features.

Methods

The participants (n = 52) included 13 DCC^+/− mutation carriers with mirror movements, 7 DCC^+/− mutation carriers without mirror movements, 13 relatives without the mutation or mirror movements, and 19 unrelated healthy volunteers. The multimodal approach comprised quantitative real time polymerase chain reaction, transcranial magnetic stimulation (TMS), functional magnetic resonance imaging (fMRI) under resting and task conditions, and measures of white matter integrity.

Results

Mirror movements were associated with reduced DCC mRNA expression, increased ipsilateral TMS‐induced motor evoked potentials, increased fMRI responses in the mirroring M1 and cerebellum, and markedly reduced interhemispheric inhibition. The DCC^+/− mutation, irrespective of mirror movements, was associated with reduced functional connectivity and white matter integrity.

Interpretation

Diverse connectivity abnormalities were identified in mutation carriers with and without mirror movements, but corticospinal effects and decreased peripheral DCC mRNA appeared driven by the mirror movement phenotype. ANN NEUROL 2019;85:433–442.

Structural Neural Correlates of Physiological Mirror Activity During Isometric Contractions of Non-Dominant Hand Muscles

Mirror Activity (MA) describes involuntarily occurring muscular activity in contralateral homologous limbs during unilateral movements. This phenomenon has not only been reported in patients with neurological disorders (i.e. Mirror Movements) but has also been observed in healthy adults referred to as physiological Mirror Activity (pMA). However, despite recent hypotheses, the underlying neural mechanisms and structural correlates of pMA still remain insufficiently described. We investigated the structural correlates of pMA during isometric contractions of hand muscles with increasing force demands on a whole-brain level by means of voxel-based morphometry (VBM) and tract-based spatial statistics (TBSS). We found significant negative correlations between individual tendencies to display pMA and grey matter volume (GMV) in the right anterior cingulate cortex (ACC) as well as fractional anisotropy (FA) of white matter (WM) tracts of left precuneus (PrC) during left (non-dominant) hand contractions. No significant structural associations for contractions of the right hand were found. Here we extend previously reported functional associations between ACC/PrC and the inhibtion of intrinsically favoured mirror-symmetrical movement tendencies to an underlying structural level. We provide novel evidence that the individual structural state of higher order motor/executive areas upstream of primary/secondary motor areas might contribute to the phenomen of pMA.

DCC mutation update: Congenital mirror movements, isolated agenesis of the corpus callosum, and developmental split brain syndrome

The deleted in colorectal cancer (DCC) gene encodes the netrin-1 (NTN1) receptor DCC, a transmembrane protein required for the guidance of commissural axons. Germline DCC mutations disrupt the development of predominantly commissural tracts in the central nervous system (CNS) and cause a spectrum of neurological disorders. Monoallelic, missense, and predicted loss-of-function DCC mutations cause congenital mirror movements, isolated agenesis of the corpus callosum (ACC), or both. Biallelic, predicted loss-of-function DCC mutations cause developmental split brain syndrome (DSBS). Although the underlying molecular mechanisms leading to disease remain poorly understood, they are thought to stem from reduced or perturbed NTN1 signaling. Here, we review the 26 reported DCC mutations associated with abnormal CNS development in humans, including 14 missense and 12 predicted loss-of-function mutations, and discuss their associated clinical characteristics and diagnostic features. We provide an update on the observed genotype-phenotype relationships of congenital mirror movements, isolated ACC and DSBS, and correlate this to our current understanding of the biological function of DCC in the development of the CNS. All mutations and their associated phenotypes were deposited into a locus-specific LOVD (https://databases.lovd.nl/shared/genes/DCC).

Mutations in the netrin-1 gene cause congenital mirror movements

Netrin-1 is a secreted protein that was first identified 20 years ago as an axon guidance molecule that regulates midline crossing in the CNS. It plays critical roles in various tissues throughout development and is implicated in tumorigenesis and inflammation in adulthood. Despite extensive studies, no inherited human disease has been directly associated with mutations in NTN1, the gene coding for netrin-1. Here, we have identified 3 mutations in exon 7 of NTN1 in 2 unrelated families and 1 sporadic case with isolated congenital mirror movements (CMM), a disorder characterized by involuntary movements of one hand that mirror intentional movements of the opposite hand. Given the diverse roles of netrin-1, the absence of manifestations other than CMM in NTN1 mutation carriers was unexpected. Using multimodal approaches, we discovered that the anatomy of the corticospinal tract (CST) is abnormal in patients with NTN1-mutant CMM. When expressed in HEK293 or stable HeLa cells, the 3 mutated netrin-1 proteins were almost exclusively detected in the intracellular compartment, contrary to WT netrin-1, which is detected in both intracellular and extracellular compartments. Since netrin-1 is a diffusible extracellular cue, the pathophysiology likely involves its loss of function and subsequent disruption of axon guidance, resulting in abnormal decussation of the CST.

Pre-movement planning processes in people with congenital mirror movements

OBJECTIVE

Pre-movement processes were investigated in people with Congenital mirrormovement (CMM), a rare disorder in which bilateral movement (mirroring) occurs in the upper distal extremities (primarily the hands and fingers) during intended unilateral movements. Abnormal density of ipsilateral corticospinal projections is an established hallmark of CMM. This study tested whether the Lateralised Readiness Potential (LRP), which reflects movement planning and readiness, is also abnormal in people with CMM.

METHODS

Twenty-eight neurologically-normal controls and 8 people with CMM were tested on a unimanual Go/No-go task while electroencephalography (EEG) was recorded to assess the LRP.

RESULTS

No significant group differences were found in reaction time (RT). However, significantly smaller LRP amplitudes were found, on average, in the CMM group compared to Controls at central-motor (C3,C4) sites in stimulus-locked and response-locked epochs; similar group differences were also found at further frontal sites (F3,F4) during response-locked epochs.

CONCLUSIONS

Abnormal brain activity in pre-movement processes associated with response planning and preparation is present in people with CMM.

SIGNIFICANCE

Aberrant bilateral activity during pre-movement processes is clearly implicated; whether part of the etiology of CMM, or as a mechanism of neuro-compensation, is not yet known.

Pitfalls in Organizational Neuroscience: A Critical Review and Suggestions for Future Research

The potential of neuroscience to be a viable framework for studying human behavior in organizations depends on scholars’ ability to evaluate, design, analyze, and accurately interpret neuroscientific research. Prior to the publishing of this special issue, relatively little guidance has been available in the management literature for scholars seeking to integrate neuroscience and organization science in a balanced, informative and methodologically rigorous manner. In response to this need, we address design logic and inferential issues involved in evaluating and conducting neuroscience research capable of informing organizational science. Specifically, neuroscience methods of functional magnetic resonance imaging, electroencephalography, lesion studies, transcranial magnetic stimulation, and transcranial direct current stimulation are reviewed, with attention to how these methods might be combined to achieve convergent evidence. We then discuss strengths and limitations of various designs, highlighting the issue of reverse inference as precarious yet necessary for organizational neuroscience. We offer solutions for addressing limitations related to reverse inference, and propose features that allow stronger inferences to be made. The article concludes with a review of selected empirical work in organizational neuroscience in light of these critical design features.

Whole-exome sequencing of 228 patients with sporadic Parkinson's disease

Parkinson's disease (PD) is the most common neurodegenerative movement disorder, affecting 1% of the population over 65 years characterized clinically by both motor and non-motor symptoms accompanied by the preferential loss of dopamine neurons in the substantia nigra pars compacta. Here, we sequenced the exomes of 244 Parkinson's patients selected from the Oxford Parkinson's Disease Centre Discovery Cohort and, after quality control, 228 exomes were available for analyses. The PD patient exomes were compared to 884 control exomes selected from the UK10K datasets. No single non-synonymous (NS) single nucleotide variant (SNV) nor any gene carrying a higher burden of NS SNVs was significantly associated with PD status after multiple-testing correction. However, significant enrichments of genes whose proteins have roles in the extracellular matrix were amongst the top 300 genes with the most significantly associated NS SNVs, while regions associated with PD by a recent Genome Wide Association (GWA) study were enriched in genes containing PD-associated NS SNVs. By examining genes within GWA regions possessing rare PD-associated SNVs, we identified RAD51B. The protein-product of RAD51B interacts with that of its paralogue RAD51, which is associated with congenital mirror movements phenotypes, a phenotype also comorbid with PD.

A novel role for the DNA repair gene Rad51 in Netrin-1 signalling

Mutations in RAD51 have recently been linked to human Congenital Mirror Movements (CMM), a developmental disorder of the motor system. The only gene previously linked to CMM encodes the Netrin-1 receptor DCC, which is important for formation of corticospinal and callosal axon tracts. Thus, we hypothesised that Rad51 has a novel role in Netrin-1-mediated axon development. In mouse primary motor cortex neurons, Rad51 protein was redistributed distally down the axon in response to Netrin-1, further suggesting a functional link between the two. We next manipulated Rad51 expression, and assessed Netrin-1 responsiveness. Rad51 siRNA knockdown exaggerated Netrin-1-mediated neurite branching and filopodia formation. RAD51 overexpression inhibited these responses, whereas overexpression of the CMM-linked R250Q mutation, a predicted loss-of-function, had no effect. Thus, Rad51 appears to negatively regulate Netrin-1 signalling. Finally, we examined whether Rad51 might operate by modulating the expression of the Unc5 family, known negative regulators of Netrin-1-responsiveness. Unc5b and Unc5c transcripts were downregulated in response to Rad51 knockdown, and upregulated with RAD51 overexpression, but not R250Q. Thus, Rad51 negatively regulates Netrin-1 signalling, at least in part, by modulating the expression of Unc5s. Imbalance of positive and negative influences is likely to lead to aberrant motor system development resulting in CMMs.

Congenital Mirror Movements Due to RAD51: Cosegregation with a Nonsense Mutation in a Norwegian Pedigree and Review of the Literature

Background

Autosomal dominant congenital mirror movements (CMM) is a neurodevelopmental disorder characterized by early onset involuntary movements of one side of the body that mirror intentional movements on the contralateral side; these persist throughout life in the absence of other neurological symptoms. The main culprit genes responsible for this condition are RAD51 and DCC. This condition has only been reported in a few families, and the molecular mechanisms linking RAD51 mutations and mirror movements (MM) are poorly understood.

Methods

We collected demographic, clinical, and genetic data of a new family with CMM due to a truncating mutation of RAD51. We reviewed the literature to identify all reported patients with CMM due to RAD51 mutations.

Results

We identified a heterozygous nonsense mutation c.760C>T (p.Arg254*) in eight subjects: four with obvious and disabling MM, and four with a mild phenotype. Including our new family, we identified 32 patients from 6 families with CMM linked to RAD51 variants.

Discussion

Our findings further support the involvement of RAD51 in CMM pathogenesis. Possible molecular mechanisms involved in CMM pathogenesis are discussed.

Congenital Mirror Movements in Gorlin Syndrome: A Case Report With DTI and Functional MRI Features

Congenital mirror movements are rare conditions that define the inability to perform unimanual movements. Gorlin syndrome, also known as nevoid basal cell carcinoma syndrome, is a genetic disorder with multiple nevi predisposing to basal cell carcinoma, odontogenic keratocysts, and skeletal malformations. Herein we report on an adolescent patient with Gorlin syndrome and coexisting congenital mirror movements. To our knowledge, this is the first patient in the literature who has both of these very rare conditions.