Cutaneous venous malformations presenting in an adolescent boy: Cerebral cavernous malformation syndrome

Cerebral cavernous malformations (CCM) are collections of enlarged capillaries with irregular structure, located in the brain or spinal cord, that can be life-threatening. We describe a neurologically asymptomatic 15-year-old boy who presented with cutaneous venous malformations (CVM) that developed in adolescence. Owing to his family history of CCM, genetic testing was obtained and confirmed a new mutation in the CCM3 (PDCD10) gene. Brain imaging showed multiple CCM. Although currently asymptomatic, he will continue to be monitored annually by neurology to assess for symptoms of intracranial hemorrhage (ICH) that would warrant investigation with MRI.     

Longitudinal Positron Emission Tomography of Dopamine Synthesis in Subjects with GBA1 Mutations

Mutations in GBA1, the gene mutated in Gaucher disease, are a common genetic risk factor for Parkinson disease, although the penetrance is low. We performed [¹⁸F]-fluorodopa positron emission tomography studies of 57 homozygous and heterozygous GBA1 mutation carriers (15 with parkinsonism) and 98 controls looking for early indications of dopamine loss using voxelwise analyses to identify group differences in striatal [¹⁸F]-fluorodopa uptake (K_i). Forty-eight subjects were followed longitudinally. Cross-sectional and longitudinal comparisons of K_i and K_i change found significant effects of Parkinson disease. However, at baseline and over time, striatal [¹⁸F]-fluorodopa uptake in mutation carriers without parkinsonism did not significantly differ from controls. ANN NEUROL 2020;87:652–657     

Group leader and participant perceptions of Balancing Everyday Life,a group-based lifestyle intervention for mental health service users

Abstract

Background: There exist few recovery and occupation-based interventions for mental health service users. Balancing Everyday Life (BEL) is a new occupation-based lifestyle intervention that was created to fill this need.

Aim: To gain group leaders’ and participants’ perspectives of the BEL intervention content and format, including factors that helped, hindered, and could be improved.

Methods: A constructivist grounded theory method guided data collection and analysis. Interviews took place with 12 BEL group leaders and 19 BEL participants from out-patient psychiatry settings and community-based day centers in Sweden.

Results: BEL’s structure and content were appreciated, yet flexibility was desired to adapt to participant needs. BEL could act as a bridge, helping participants connect with others, and to a more engaged and balanced everyday life. Facilitating factors included a person-focused (versus illness-focused) approach, physical and emotional environments, and connection. Barriers included room resources. More sessions were desired for the intervention.

Conclusion: Group leaders and participants experienced BEL as a useful tool to instigate meaningful change and connection in the participants’ lives. The combination of a positive person-focused approach and group support was appreciated. These results could inform future research, evaluation, and development of occupation-focused lifestyle interventions for mental health service users.     

Genotype-phenotype correlation and molecular heterogeneity in pyruvate kinase deficiency

Pyruvate kinase (PK) deficiency is a rare recessive congenital hemolytic anemia caused by mutations in the PKLR gene. This study reports the molecular features of 257 patients enrolled in the PKD Natural History Study. Of the 127 different pathogenic variants detected, 84 were missense and 43 non-missense, including 20 stop-gain, 11 affecting splicing, five large deletions, four in-frame indels, and three promoter variants. Within the 177 unrelated patients, 35 were homozygous and 142 compound heterozygous (77 for two missense, 48 for one missense and one non-missense, and 17 for two non-missense variants); the two most frequent mutations were p.R510Q in 23% and p.R486W in 9% of mutated alleles. Fifty-five (21%) patients were found to have at least one previously unreported variant with 45 newly described mutations. Patients with two non-missense mutations had lower hemoglobin levels, higher numbers of lifetime transfusions, and higher rates of complications including iron overload, extramedullary hematopoiesis, and pulmonary hypertension. Rare severe complications, including lower extremity ulcerations and hepatic failure, were seen more frequently in patients with non-missense mutations or with missense mutations characterized by severe protein instability. The PKLR genotype did not correlate with the frequency of complications in utero or in the newborn period. With ICCs ranging from 0.4 to 0.61, about the same degree of clinical similarity exists within siblings as it does between siblings, in terms of hemoglobin, total bilirubin, splenectomy status, and cholecystectomy status. Pregnancy outcomes were similar across genotypes in PK deficient women. This report confirms the wide genetic heterogeneity of PK deficiency.     

X-ray crystallographic and EPR spectroscopic analysis of HydG,a maturase in [FeFe]-hydrogenase H-cluster assembly

Hydrogenases use complex metal cofactors to catalyze the reversible formation of hydrogen. In [FeFe]-hydrogenases, the H-cluster cofactor includes a diiron subcluster containing azadithiolate, three CO, and two CN⁻ ligands. During the assembly of the H cluster, the radical S-adenosyl methionine (SAM) enzyme HydG lyses the substrate tyrosine to yield the diatomic ligands. These diatomic products form an enzyme-bound Fe(CO)_x(CN)_y synthon that serves as a precursor for eventual H-cluster assembly. To further elucidate the mechanism of this complex reaction, we report the crystal structure and EPR analysis of HydG. At one end of the HydG (βα)₈ triosephosphate isomerase (TIM) barrel, a canonical [4Fe-4S] cluster binds SAM in close proximity to the proposed tyrosine binding site. At the opposite end of the active-site cavity, the structure reveals the auxiliary Fe-S cluster in two states: one monomer contains a [4Fe-5S] cluster, and the other monomer contains a [5Fe-5S] cluster consisting of a [4Fe-4S] cubane bridged by a μ₂-sulfide ion to a mononuclear Fe²⁺ center. This fifth iron is held in place by a single highly conserved protein-derived ligand: histidine 265. EPR analysis confirms the presence of the [5Fe-5S] cluster, which on incubation with cyanide, undergoes loss of the labile iron to yield a [4Fe-4S] cluster. We hypothesize that the labile iron of the [5Fe-5S] cluster is the site of Fe(CO)_x(CN)_y synthon formation and that the limited bonding between this iron and HydG may facilitate transfer of the intact synthon to its cognate acceptor for subsequent H-cluster assembly.The assembly of the [FeFe]-hydrogenase diiron subcluster (1, 2) requires three maturase proteins, HydE, HydF, and HydG (3), and in vitro, they can assemble an active hydrogenase (4). The sequence and structure of the maturase HydE (5) indicates that it is a member of the radical S-adenosyl methionine (SAM) superfamily, although the biochemical function of HydE has not been experimentally determined. The GTPase HydF (6, 7) has been shown to transfer synthetic (8) or biologically derived (7, 9) diiron subclusters into apo-hydrogenase, suggesting that HydF functions as a template for diiron subcluster assembly. The tyrosine lyase HydG is also a member of the radical SAM superfamily and uses SAM and a reductant (such as dithionite) to cleave the Cα–Cβ bond of tyrosine, yielding p-cresol as the side chain-derived byproduct (10) and fragmenting the amino acid moiety into cyanide (CN⁻) (11) and carbon monoxide (CO) (12), which are ultimately incorporated as ligands in the H cluster of the [FeFe]-hydrogenase HydA (4). Two site-differentiated [4Fe-4S] clusters in HydG have been identified using a combination of spectroscopy and site-directed mutagenesis (12–16). The cluster bound close to the N terminus ([4Fe-4S]_RS) by the CX₃CX₂C cysteine triad motif (SI Appendix, Fig. S1) is typical of the radical SAM superfamily (17, 18) and has been shown to catalyze the reductive cleavage of SAM (11, 13). The resultant highly reactive 5′-deoxyadenosyl radical is thought to abstract a hydrogen atom from tyrosine, thereby inducing Cα–Cβ-bond homolysis with release of dehydroglycine (DHG) and the spectroscopically characterized 4-oxidobenzyl radical anion (16), which is quenched to yield p-cresol (Fig. 1A, step A). The second (auxiliary) Fe-S cluster is proposed to promote the conversion of DHG into CO and CN⁻ (Fig. 1A, step B) (13, 16). Two intermediates have been observed by stopped-flow IR spectroscopic analysis (19): an enzyme-bound organometallic species (complex A) (Fig. 1A, 4) that converts to a species that features an Fe(CO)₂(CN) moiety (complex B) (Fig. 1A, 5). These results, combined with ⁵⁷Fe electron-nuclear double resonance (ENDOR) studies that showed that iron from HydG is incorporated into mature hydrogenase, led to the proposal that an organometallic synthon with a minimum stoichiometry of [Fe(CO)₂CN] is synthesized at the auxiliary cluster of HydG and eventually transferred to apo-hydrogenase (19).Open in a separate windowFig. 1.Overall [FeFe]-hydrogenase H-cluster assembly and structure of TiHydG. (A) Formation of the Fe(CO)₂CN synthon is proposed to occur at the auxiliary cluster of HydG (square brackets). (B) Overall fold of HydG with an end-on view of the TIM barrel showing the radical SAM core (green), the N-terminal extension (pink), and the C-terminal extension (blue). Monomer A is shown and contains a [4Fe-4S] cluster to catalyze the formation of the 5′-deoxyadenosyl radical from SAM and a [5Fe-5S] auxiliary cluster proposed to promote the conversion of DHG into cyanide and carbon monoxide. (C) The position of the two Fe-S clusters in TiHydG. The strands of the TIM barrel are shown. The orientation is rotated 90° from B.Herein, we report the crystal structure of Thermoanaerobacter italicus HydG (TiHydG) complexed with SAM (the Protein Data Bank ID code for the structure of HydG is 4WCX). The structure, which contains two HydG monomers per asymmetric unit, reveals the auxiliary Fe-S cluster in two states: one monomer contains a [4Fe-5S] cluster, and the other monomer contains a structurally unprecedented [5Fe-5S] cluster consisting of a [4Fe-4S] cubane bridged by a μ₂-sulfide to a mononuclear Fe(II) center (which we term the labile iron). To supplement the crystallographic studies of TiHydG, we also report EPR spectroscopic studies of Shewanella oneidensis HydG (SoHydG) that provide solution-state characterization of the [5Fe-5S] cluster and show its conversion to a [4Fe-4S] cluster in the presences of exogenous cyanide. Taken together, these results support a proposed mechanism for [FeFe]-hydrogenase maturation in which the labile iron of the [5Fe-5S] cluster is the site for Fe(CO)_x(CN)_y synthon assembly.