Biochemical analysis of novel NAA10 variants suggests distinct pathogenic mechanisms involving impaired protein N-terminal acetylation.

NAA10 is the catalytic subunit of the N-terminal acetyltransferase complex, NatA, which is responsible for N-terminal acetylation of nearly half the human proteome. Since 2011, at least 21 different NAA10 missense variants have been reported as pathogenic in humans. The clinical features associated with this X-linked condition vary, but commonly described features include developmental delay, intellectual disability, cardiac anomalies, brain abnormalities, facial dysmorphism and/or visual impairment. Here, we present eight individuals from five families with five different de novo or inherited NAA10 variants. In order to determine their pathogenicity, we have performed biochemical characterisation of the four novel variants c.16G>C p.(A6P), c.235C>T p.(R79C), c.386A>C p.(Q129P) and c.469G>A p.(E157K). Additionally, we clinically describe one new case with a previously identified pathogenic variant, c.384T>G p.(F128L). Our study provides important insight into how different NAA10 missense variants impact distinct biochemical functions of NAA10 involving the ability of NAA10 to perform N-terminal acetylation. These investigations may partially explain the phenotypic variability in affected individuals and emphasise the complexity of the cellular pathways downstream of NAA10.

Esophageal atresia/tracheoesophageal fistula and proximal symphalangism in a patient with a NOG nonsense mutation.

Esophageal atresia and tracheoesophageal fistula (EA/TEF) are relatively common malformations of the human foregut. The etiology remains incompletely understood with genetic causes identified in a small minority of affected patients. We present the case of a newborn with type C EA/TEF along with proximal symphalangism found to have a de novo NOG nonsense mutation. Patients with chromosome 17q deletions including the NOG gene have previously been reported to have EA/TEF but mutations in the gene have not been identified in patients with this malformation. This case provides evidence that haploinsufficiency for NOG may be the cause for EA/TEF in the 17q deletion syndrome and suggests that the clinical spectrum of NOG-related symphalangism spectrum disorders may include EA/TEF.

NRAS associated RASopathy and embryonal rhabdomyosarcoma.

RASopathies are a group of phenotypically overlapping disorders that arise from dysregulation of the RAS/MAPK pathway. These disorders include Noonan syndrome, Costello syndrome, cardiofaciocutaneous syndrome, and neurofibromatosis-Type 1. While somatic mutations in the three human Ras genes (KRAS, HRAS, and NRAS) are a common finding in a variety of cancers, germline mutations in each of the these genes cause developmental RASopathy phenotypes with mutations in specific genes typically correlating with specific phenotypes. We present the case of a germline heterozygous NRAS mutation producing a severe phenotype involving embryonal rhabdomyosarcoma, severe intellectual disability, and numerous melanocytic nevi in addition to more typical manifestations of Noonan syndrome. Additionally, the specific p.G12R NRAS mutation in this case is a common somatic mutation in cancer cells, and analysis of previously reported NRAS-RASopathy cases suggests that mutations at traditionally oncogenic codons are associated with elevated cancer risk not present with mutations at other sites.

Congenital lumbar hernia-A feature of diabetic embryopathy?

Congenital lumbar hernia is a rare anomaly consisting of protrusion of abdominal organs or extraperitoneal tissue through a defect in the lateral abdominal wall. The majority of affected patients have additional anomalies in a pattern described as the lumbocostovertebral syndrome. We report four patients born to mothers with poorly controlled diabetes with congenital lumbar hernia. All patients exhibited features of lumbocostovertebral syndrome with lumbar hernia, multiple vertebral segmentation anomalies in the lower thoracic and/or upper lumbar spine, rib anomalies, and unilateral renal agenesis. Additional anomalies present in the patients included preaxial hallucal polydactyly, abnormal situs, and sacral dysgenesis, anomalies known to be associated with diabetic embryopathy. At least 11 other patients have been previously reported with the lumbocostovertebral syndrome in the setting of maternal diabetes. We suggest that congenital lumbar hernia and the lumbocostovertebral syndrome are related to diabetic embryopathy.

De novo mutations in beta-catenin (CTNNB1) appear to be a frequent cause of intellectual disability: expanding the mutational and clinical spectrum.

Recently, de novo heterozygous loss-of-function mutations in beta-catenin (CTNNB1) were described for the first time in four individuals with intellectual disability (ID), microcephaly, limited speech and (progressive) spasticity, and functional consequences of CTNNB1 deficiency were characterized in a mouse model. Beta-catenin is a key downstream component of the canonical Wnt signaling pathway. Somatic gain-of-function mutations have already been found in various tumor types, whereas germline loss-of-function mutations in animal models have been shown to influence neuronal development and maturation. We report on 16 additional individuals from 15 families in whom we newly identified de novo loss-of-function CTNNB1 mutations (six nonsense, five frameshift, one missense, two splice mutation, and one whole gene deletion). All patients have ID, motor delay and speech impairment (both mostly severe) and abnormal muscle tone (truncal hypotonia and distal hypertonia/spasticity). The craniofacial phenotype comprised microcephaly (typically -2 to -4 SD) in 12 of 16 and some overlapping facial features in all individuals (broad nasal tip, small alae nasi, long and/or flat philtrum, thin upper lip vermillion). With this detailed phenotypic characterization of 16 additional individuals, we expand and further establish the clinical and mutational spectrum of inactivating CTNNB1 mutations and thereby clinically delineate this new CTNNB1 haploinsufficiency syndrome.

Truncating mutations in the last exon of NOTCH3 cause lateral meningocele syndrome.

Lateral meningocele syndrome (LMS, OMIM%130720), also known as Lehman syndrome, is a very rare skeletal disorder with facial anomalies, hypotonia and meningocele-related neurologic dysfunction. The characteristic lateral meningoceles represent the severe end of the dural ectasia spectrum and are typically most severe in the lower spine. Facial features of LMS include hypertelorism and telecanthus, high arched eyebrows, ptosis, midfacial hypoplasia, micrognathia, high and narrow palate, low-set ears and a hypotonic appearance. Hyperextensibility, hernias and scoliosis reflect a connective tissue abnormality, and aortic dilation, a high-pitched nasal voice, wormian bones and osteolysis may be present. Lateral meningocele syndrome has phenotypic overlap with Hajdu-Cheney syndrome. We performed exome resequencing in five unrelated individuals with LMS and identified heterozygous truncating NOTCH3 mutations. In an additional unrelated individual Sanger sequencing revealed a deleterious variant in the same exon 33. In total, five novel de novo NOTCH3 mutations were identified in six unrelated patients. One had a 26 bp deletion (c.6461_6486del, p.G2154fsTer78), two carried the same single base pair insertion (c.6692_93insC, p.P2231fsTer11), and three individuals had a nonsense point mutation at c.6247A > T (pK2083*), c.6663C > G (p.Y2221*) or c.6732C > A, (p.Y2244*). All mutations cluster into the last coding exon, resulting in premature termination of the protein and truncation of the negative regulatory proline-glutamate-serine-threonine rich PEST domain. Our results suggest that mutant mRNA products escape nonsense mediated decay. The truncated NOTCH3 may cause gain-of-function through decreased clearance of the active intracellular product, resembling NOTCH2 mutations in the clinically related Hajdu-Cheney syndrome and contrasting the NOTCH3 missense mutations causing CADASIL.

Mutation update and genotype-phenotype correlations of novel and previously described mutations in TPM2 and TPM3 causing congenital myopathies.

Mutations affecting skeletal muscle isoforms of the tropomyosin genes may cause nemaline myopathy, cap myopathy, core-rod myopathy, congenital fiber-type disproportion, distal arthrogryposes, and Escobar syndrome. We correlate the clinical picture of these diseases with novel (19) and previously reported (31) mutations of the TPM2 and TPM3 genes. Included are altogether 93 families: 53 with TPM2 mutations and 40 with TPM3 mutations. Thirty distinct pathogenic variants of TPM2 and 20 of TPM3 have been published or listed in the Leiden Open Variant Database (http://www.dmd.nl/). Most are heterozygous changes associated with autosomal-dominant disease. Patients with TPM2 mutations tended to present with milder symptoms than those with TPM3 mutations, DA being present only in the TPM2 group. Previous studies have shown that five of the mutations in TPM2 and one in TPM3 cause increased Ca(2+) sensitivity resulting in a hypercontractile molecular phenotype. Patients with hypercontractile phenotype more often had contractures of the limb joints (18/19) and jaw (6/19) than those with nonhypercontractile ones (2/22 and 1/22), whereas patients with the non-hypercontractile molecular phenotype more often (19/22) had axial contractures than the hypercontractile group (7/19). Our in silico predictions show that most mutations affect tropomyosin-actin association or tropomyosin head-to-tail binding.

Loss of symmetric cell division of apical neural progenitors drives DENND5A-related developmental and epileptic encephalopathy.

Developmental and epileptic encephalopathies (DEEs) are a heterogenous group of epilepsies in which altered brain development leads to developmental delay and seizures, with the epileptic activity further negatively impacting neurodevelopment. Identifying the underlying cause of DEEs is essential for progress toward precision therapies. Here we describe a group of individuals with biallelic variants in DENND5A and determine that variant type is correlated with disease severity. We demonstrate that DENND5A interacts with MUPP1 and PALS1, components of the Crumbs apical polarity complex, which is required for both neural progenitor cell identity and the ability of these stem cells to divide symmetrically. Induced pluripotent stem cells lacking DENND5A fail to undergo symmetric cell division during neural induction and have an inherent propensity to differentiate into neurons, and transgenic DENND5A mice, with phenotypes like the human syndrome, have an increased number of neurons in the adult subventricular zone. Disruption of symmetric cell division following loss of DENND5A results from misalignment of the mitotic spindle in apical neural progenitors. A subset of DENND5A is localized to centrosomes, which define the spindle poles during mitosis. Cells lacking DENND5A orient away from the proliferative apical domain surrounding the ventricles, biasing daughter cells towards a more fate-committed state and ultimately shortening the period of neurogenesis. This study provides a mechanism behind DENND5A-related DEE that may be generalizable to other developmental conditions and provides variant-specific clinical information for physicians and families.

Battlefield Triage and Resource Allocation during a Pandemic: Learning from the Past and Adapting for the Future.

The principle of medical triage, where patients are sorted into categories to guide the order in which they receive treatment, dates back to Baron Dominique Jean Larrey, the surgeon general of Napolean's armies. The concept evolved with military conflicts throughout the 19th century, was subsequently adapted to situations off the battlefield, and is now widely practiced where resources are limited.2 Military medical providers are taught triage principles early in their careers and its use is routinely integrated into military training scenarios and operational planning.

Mupirocin resistance related to increasing mupirocin use in clinical isolates of methicillin-resistant Staphylococcus aureus in a pediatric population.

We investigated the proportion of methicillin-resistant Staphylococcus aureus (MRSA) isolates from pediatric patients demonstrating mupirocin resistance related to mupirocin use at our institution. No mupirocin resistance was found in 98% of isolates, whereas mupirocin prescriptions increased by 110%. Resistance rates remained low despite the increasing use of mupirocin.

Uncertainty: An Uncomfortable Companion to Decision-making for Infants.

Although parents are typically the most appropriate decision-makers for their children, there are limits to this authority. Medical providers may be ethically obligated to seek state intervention against a parental decision if the parent places a child at significant and imminent risk of serious harm. When parents make medical decisions for their children, they assess both the projected benefits and risks of their choices for their family. These assessments are impacted by uncertainty, which is a common feature of neonatal intensive care. The relative presence or absence of uncertainty may impact perceptions of parental decisions and a medical provider's decision to seek state intervention to overrule parents. In this article, we propose a model integrating prognostic uncertainty into pediatric decision-making that may aid providers in such assessments. We will demonstrate how to apply this model to 3 neonatal cases and propose that the presence of greater uncertainty ought to permit parents greater latitude to incorporate family values into their decision-making even if these decisions are contradictory to the recommendations of the medical team.

Mupirocin resistance screening of methicillin-resistant Staphylococcus aureus isolates at Madigan Army Medical Center.

Mupirocin is an antibiotic used for eradication and infection control of methicillin-resistant Staphylococcus aureus (MRSA). Mupirocin binds to the bacterial isoleucyl tRNA synthetase, thus disrupting bacterial protein synthesis. Four hundred nine MRSA clinical isolates collected in 2006 and 2007 at Madigan Army Medical Center were screened for mupirocin resistance by E test and polymerase chain reaction; 7 MRSA isolates (1.7%) were found to be fully resistant to mupirocin (minimum inhibitory concentration [MIC] by E test: > 1,024 microg/mL), 10 isolates (2.4%) had MIC values of 1 to 32 microg/mL, while 392 MRSA isolates (95.9%) had MIC values of < 1 microg/mL. No trend of increased mupirocin resistance was found when compared with subsequent years. These results show that mupirocin remains a valid infection control measure due to its unique mechanism of action and the high susceptibility rate of MRSA isolates. In addition, rapid screening by polymerase chain reaction of MRSA shows promise in assessing the fully resistant mupirocin phenotype.

Two novel RAD21 mutations in patients with mild Cornelia de Lange syndrome-like presentation and report of the first familial case.

Cornelia de Lange syndrome (CdLS) is a developmental disorder characterized by limb reduction defects, characteristic facial features and impaired cognitive development. Mutations in the NIPBL gene predominate; however, mutations in other cohesin complex genes have also been implicated, particularly in atypical and mild CdLS cases. Missense mutations and whole gene deletions in RAD21 have been identified in children with growth retardation, minor skeletal anomalies and facial features that overlap findings in individuals with CdLS. We report the first intragenic deletion and frameshift mutations identified in RAD21 in two patients presenting with atypical CdLS. One patient had an in-frame deletion of exon 13, while the second patient had a c.592_593dup frameshift mutation. The first patient presented with developmental delay, hypospadias, inguinal hernia and dysmorphic features while, the second patient presented with developmental delay, characteristic facial features, hirsutism, and hand and feet anomalies, with the first patient being milder than the second. The in-frame deletion mutation was found to be inherited from the mother who had a history of melanoma and other unspecified medical problems. This study expands the spectrum of RAD21 mutations and emphasizes the clinical utility of performing RAD21 mutation analysis in patients presenting with atypical forms of CdLS. Moreover, the variability of clinical presentation within families and low penetrance of mutations as well as the significance of performing molecular genetic testing in mildly affected patients are discussed.