Creatine Transporter Defect Diagnosed by Proton NMR Spectroscopy in Males With Intellectual Disability

Creatine deficiency syndrome due to mutations in X-linked SLC6A8 gene results in nonspecific intellectual disability (ID). Diagnosis cannot be established on clinical grounds and is often based on the assessment of brain creatine levels by magnetic resonance spectroscopy (MRS). Considering high costs of MRS and necessity of sedation, this technique cannot be used as a first level-screening test. Likewise, gene test analysis is time consuming and not easily accessible to all laboratories. In this article feasibility of urine analysis (creatine/creatinine (Cr/Crn) ratio) performed by nuclear magnetic resonance (NMR) as a first level-screening test is explored. Before running a systematic selection of cases a preliminary study for further molecular analysis is shown. NMR urine spectra (n = 1,347) of male patients with an ID without a clinically recognizable syndrome were measured. On the basis of abnormal Cr/Crn ratio, three patients with the highest values were selected for molecular analysis. A confirmatory second urine test was positive in two patients and diagnosis was further confirmed by a decreased brain creatine level and by SLC6A8 gene analysis. A de novo mutation was identified in one. Another patient inherited a novel mutation from the mother who also has a mild ID. A repeat urine test was negative in the third patient and accordingly creatine level in the brain and SLC6A8 gene analysis both gave a normal result. We conclude that Cr/Crn ratio measured by NMR for male patients represents a rapid and useful first level screening test preceding molecular analysis. © 2011 Wiley-Liss, Inc

SPTBN5, Encoding the βV-Spectrin Protein, Leads to a Syndrome of Intellectual Disability, Developmental Delay, and Seizures

Whole exome sequencing has provided significant opportunities to discover novel candidate genes for intellectual disability and autism spectrum disorders. Variants in the spectrin genes SPTAN1, SPTBN1, SPTBN2, and SPTBN4 have been associated with neurological disorders; however, SPTBN5 gene-variants have not been associated with any human disorder. This is the first report that associates SPTBN5 gene variants (ENSG00000137877: c.266A>C; p.His89Pro, c.9784G>A; p.Glu3262Lys, c.933C>G; p.Tyr311Ter, and c.8809A>T; p.Asn2937Tyr) causing neurodevelopmental phenotypes in four different families. The SPTBN5-associated clinical traits in our patients include intellectual disability (mild to severe), aggressive tendencies, accompanied by variable features such as craniofacial and physical dysmorphisms, autistic behavior, and gastroesophageal reflux. We also provide a review of the existing literature related to other spectrin genes, which highlights clinical features partially overlapping with SPTBN5

Capping of the N-terminus of PSD-95 by calmodulin triggers its postsynaptic release

Postsynaptic density protein-95 (PSD-95) is a central element of the postsynaptic architecture of glutamatergic synapses. PSD-95 mediates postsynaptic localization of AMPA receptors and NMDA receptors and plays an important role in synaptic plasticity. PSD-95 is released from postsynaptic membranes in response to Ca2+ influx via NMDA receptors. Here, we show that Ca2+/calmodulin (CaM) binds at the N-terminus of PSD-95. Our NMR structure reveals that both lobes of CaM collapse onto a helical structure of PSD-95 formed at its N-terminus (residues 1-16). This N-terminal capping of PSD-95 by CaM blocks palmitoylation of C3 and C5, which is required for postsynaptic PSD-95 targeting and the binding of CDKL5, a kinase important for synapse stability. CaM forms extensive hydrophobic contacts with Y12 of PSD-95. The PSD-95 mutant Y12E strongly impairs binding to CaM and Ca 2+-induced release of PSD-95 from the postsynaptic membrane in dendritic spines. Our data indicate that CaM binding to PSD-95 serves to block palmitoylation of PSD-95, which in turn promotes Ca2+-induced dissociation of PSD-95 from the postsynaptic membrane. Synopsis Ca2+ influx promotes Ca2+/calmodulin binding to the N-terminus of PSD-95, which blocks PSD-95 palmitoylation leading to reduced retention of PSD-95 at synapses. This effect will likely decrease postsynaptic glutamate receptor content and thereby synaptic strength. Ca2+/calmodulin forms a collapsed structure around the N-terminal helix of PSD-95 that sequesters the palmitoylation sites (Cys3 and Cys5) and a key tyrosine (Tyr12). Binding of Ca2+/calmodulin to the N-terminus of PSD-95 decreases its palmitoylation to release PSD-95 from postsynaptic sites Binding of Ca 2+/calmodulin also displaces the serine/threonine kinase CDKL5 from PSD-95, which otherwise helps augment synaptic strength A point mutation of PSD-95 that prevents Ca2+/calmodulin binding turns the Ca 2+-induced reduction in PSD-95 at synapses into an increase, uncovering the existence of a second mechanism that augments postsynaptic PSD-95 enrichment upon Ca2+ influx. Ca2+ influx promotes Ca 2+/calmodulin binding to the N-terminus of PSD-95, which blocks PSD-95 palmitoylation leading to reduced retention of PSD-95 at synapses

May-Hegglin Anomaly, Sebastian Syndrome, Fechtner Syndrome, and Epstein Syndrome Are not Distinct Entities but Represent a Variable Expression of a Single Illness

May-Hegglin anomaly, Sebastian syndrome, Fechtner syndrome, and Epstein syndrome are autosomal dominant macrothrombocytopenias distinguished by different combinations of clinical and laboratory signs, such as sensorineural hearing loss, cataract, nephritis, and polymorphonuclear Döhle-like bodies. Mutations in the MYH9 gene encoding for the nonmuscle myosin heavy chain IIA (NMMHC-IIA) have been identified in all these syndromes. To understand the role of the MYH9 mutations, we report the molecular defects in 12 new cases, which together with our previous works represent a cohort of 19 families. Since no genotype-phenotype correlation was established, we performed an accurate clinical and biochemical re-evaluation of patients. In addition to macrothrombocytopenia, an abnormal distribution of NMMHC-IIA within leukocytes was observed in all individuals, including those without Döhle-like bodies. Selective, high-tone hearing deficiency and cataract was diagnosed in 83% and 23%, respectively, of patients initially referred as having May-Hegglin anomaly or Sebastian syndrome. Kidney abnormalities, such as hematuria and proteinuria, affected not only patients referred as Fechtner syndrome and Epstein syndrome but also those referred as May-Hegglin anomaly and Sebastian syndrome. These findings allowed us to conclude that May-Hegglin anomaly, Sebastian syndrome, Fechtner syndrome, and Epstein syndrome are not distinct entities but rather a single disorder with a continuous clinical spectrum varying from mild macrothrombocytopenia with leukocyte inclusions to a severe form complicated by hearing loss, cataracts, and renal failure. For this new nosologic entity, we propose the term "MHY9-related disease," which better interprets the recent knowledge in this field and identifies all patients at risk of developing renal, hearing, or visual defects

Array comparative genomic hybridization in retinoma and retinoblastoma tissues

In retinoblastoma, two RB1 mutations are necessary for tumor development. Recurrent genomic rearrangements may represent subsequent events required for retinoblastoma progression. Array-comparative genomic hybridization was carried out in 18 eye samples, 10 from bilateral and eight from unilateral retinoblastoma patients. Two unilateral cases also showed areas of retinoma. The most frequent imbalance in retinoblastomas was 6p gain (40%), followed by gains at 1q12-q25.3, 2p24.3-p24.2, 9q22.2, and 9q33.1 and losses at 11q24.3, 13q13.2-q22.3, and 16q12.1-q21. Bilateral cases showed a lower number of imbalances than unilateral cases (P = 0.002). Unilateral cases were divided into low-level (≤4) and high-level (÷7) chromosomal instability groups. The first group presented with younger age at diagnosis (mean 511 days) compared with the second group (mean 1606 days). In one retinoma case ophthalmoscopically diagnosed as a benign lesion no rearrangements were detected, whereas the adjacent retinoblastoma displayed seven aberrations. The other retinoma case identified by retrospective histopathological examination shared three rearrangements with the adjacent retinoblastoma. Two other gene-free rearrangements were retinoma specific. One rearrangement, dup5p, was retinoblastoma specific and included the SKP2 gene. Genomic profiling indicated that the first retinoma was a pretumoral lesion, whereas the other represents a subclone of cells bearing 'benign' rearrangements overwhelmed by another subclone presenting aberrations with higher 'oncogenic' potential. In summary, the present study shows that bilateral and unilateral retinoblastoma have different chromosomal instability that correlates with the age of tumor onset in unilateral cases. This is the first report of genomic profiling in retinoma tissue, shedding light on the different nature of lesions named 'retinoma'. (Cancer Sci 2009; 100: 465–471

Revised nomenclature for the mammalian long-chain acyl-CoA synthetase gene family.

By consensus, the acyl-CoA synthetase (ACS) community, with the advice of the human and mouse genome nomenclature committees, has revised the nomenclature for the mammalian long-chain acyl-CoA synthetases. ACS is the family root name, and the human and mouse genes for the long-chain ACSs are termed ACSL1,3-6 and Acsl1,3-6, respectively. Splice variants of ACSL3, -4, -5, and -6 are cataloged. Suggestions for naming other family members and for the nonmammalian acyl-CoA synthetases are made

The 2019 and 2021 International Workshops on Alport Syndrome

In 1927 Arthur Cecil Alport, a South African physician, described a British family with an inherited form of kidney disease that affected males more severely than females and was sometimes associated with hearing loss. In 1961, the eponymous name Alport syndrome was adopted. In the late twentieth century three genes responsible for the disease were discovered: COL4A3, COL4A4, and COL4A5 encoding for the α3, α4, α5 polypeptide chains of type IV collagen, respectively. These chains assemble to form heterotrimers of type IV collagen in the glomerular basement membrane. Scientists, clinicians, patient representatives and their families, and pharma companies attended the 2019 International Workshop on Alport Syndrome, held in Siena, Italy, from October 22 to 26, and the 2021 online Workshop from November 30 to December 4. The main topics included: disease re-naming, acknowledging the need to identify an appropriate term able to reflect considerable clinical variability; a strategy for increasing the molecular diagnostic rate; genotype-phenotype correlation from monogenic to digenic forms; new therapeutics and new therapeutic approaches; and gene therapy using gene editing. The exceptional collaborative climate that was established in the magical medieval setting of Siena continued in the online workshop of 2021. Conditions were established for collaborations between leading experts in the sector, including patients and drug companies, with the aim of identifying a cure for Alport syndrome