Further delineation of the rare GDACCF (global developmental delay, absent or hypoplastic corpus callosum, dysmorphic facies syndrome): genotype and phenotype of 22 patients with ZNF148 mutations.

BACKGROUND: Pathogenic variants in the zinc finger protein coding genes are rare causes of intellectual disability and congenital malformations. Mutations in the ZNF148 gene causing GDACCF syndrome (global developmental delay, absent or hypoplastic corpus callosum, dysmorphic facies; MIM #617260) have been reported in five individuals so far. METHODS: As a result of an international collaboration using GeneMatcher Phenome Central Repository and personal communications, here we describe the clinical and molecular genetic characteristics of 22 previously unreported individuals. RESULTS: The core clinical phenotype is characterised by developmental delay particularly in the domain of speech development, postnatal growth retardation, microcephaly and facial dysmorphism. Corpus callosum abnormalities appear less frequently than suggested by previous observations. The identified mutations concerned nonsense or frameshift variants that were mainly located in the last exon of the ZNF148 gene. Heterozygous deletion including the entire ZNF148 gene was found in only one case. Most mutations occurred de novo, but were inherited from an affected parent in two families. CONCLUSION: The GDACCF syndrome is clinically diverse, and a genotype-first approach, that is, exome sequencing is recommended for establishing a genetic diagnosis rather than a phenotype-first approach. However, the syndrome may be suspected based on some recurrent, recognisable features. Corpus callosum anomalies were not as constant as previously suggested, we therefore recommend to replace the term 'GDACCF syndrome' with 'ZNF148-related neurodevelopmental disorder'.

Personalized recurrence risk assessment following the birth of a child with a pathogenic de novo mutation.

Following the diagnosis of a paediatric disorder caused by an apparently de novo mutation, a recurrence risk of 1-2% is frequently quoted due to the possibility of parental germline mosaicism; but for any specific couple, this figure is usually incorrect. We present a systematic approach to providing individualized recurrence risk. By combining locus-specific sequencing of multiple tissues to detect occult mosaicism with long-read sequencing to determine the parent-of-origin of the mutation, we show that we can stratify the majority of couples into one of seven discrete categories associated with substantially different risks to future offspring. Among 58 families with a single affected offspring (representing 59 de novo mutations in 49 genes), the recurrence risk for 35 (59%) was decreased below 0.1%, but increased owing to parental mixed mosaicism for 5 (9%)-that could be quantified in semen for paternal cases (recurrence risks of 5.6-12.1%). Implementation of this strategy offers the prospect of driving a major transformation in the practice of genetic counselling.

A Facile Synthesis of Cellulose Nanofibers from Corn Cob and Rice Straw by Acid Hydrolysis Method.

Agricultural residues are suitable to make useful products that can potentially replace the non-biodegradable polymeric materials. In the present work, corn cob and rice S=straw is quantitatively transformed to cellulose by alkali treatment preceded by bleaching. The obtained cellulose is changed into nanocellulose (NC) by the acid hydrolysis method followed by ultrasonication. Further NC was characterized by FTIR to study its functional regions and XRD for crystallinity. Thermal properties have been studied using TGA/DTA. The surface morphology of nanocellulose was done using SEM and TEM. The obtained results revealed remarkable thermal stability, semi-crystalline and fibrous nature of both corn cob and rice straw. The size of the cellulose is in the nanoscale dimension. This work provides the way to utilize corn cob and rice straw as a more useful raw material for many applications.

Integrins direct Src family kinases to regulate distinct phases of oligodendrocyte development.

Specific integrins expressed on oligodendrocytes, the myelin-forming cells of the central nervous system, promote either differentiation and survival or proliferation by amplification of growth factor signaling. Here, we report that the Src family kinases (SFKs) Fyn and Lyn regulate each of these distinct integrin-driven behaviors. Fyn associates with alpha6beta1 and is required to amplify platelet-derived growth factor survival signaling, to promote myelin membrane formation, and to switch neuregulin signaling from a phosphatidylinositol 3-kinase to a mitogen-activated protein kinase pathway (thereby changing the response from proliferation to differentiation). However, earlier in the lineage Lyn, not Fyn, is required to drive alphaVbeta3-dependent progenitor proliferation. The two SFKs respond to integrin ligation by different mechanisms: Lyn, by increased autophosphorylation of a catalytic tyrosine; and Fyn, by reduced Csk phosphorylation of the inhibitory COOH-terminal tyrosine. These findings illustrate how different SFKs can act as effectors for specific cell responses during development within a single cell lineage, and, furthermore, provide a molecular mechanism to explain similar region-specific hypomyelination in laminin- and Fyn-deficient mice.

SHOX haploinsufficiency presenting with isolated short long bones in the second and third trimester.

Haploinsufficiency of the transcription factor short stature homeobox (SHOX) manifests as a spectrum of clinical phenotypes, ranging from disproportionate short stature and Madelung deformity to isolated short stature. Here, we describe five infants with molecularly confirmed diagnoses of SHOX haploinsufficiency who presented in utero with short long bones during routine antenatal scanning from as early as 19 weeks gestation. Other foetal growth parameters were normal. The molecular basis of SHOX haploinsufficiency was distinct in each case. In four cases, SHOX haploinsufficiency was inherited from a previously undiagnosed parent. In our de novo case, SHOX haploinsufficiency reflected the formation of a derivative sex chromosome during paternal meiosis. Final adult height in the SHOX-deficient parents ranged from -1.9 to -1.2 SDS. All affected parents had disproportionately short limbs and two affected mothers had bilateral Madelung deformity. To our knowledge, SHOX haploinsufficiency has not previously been reported to present in utero. Our experience illustrates that SHOX deficiency should form part of the differential diagnosis of foetal short long bones and suggests a low threshold for genetic testing. This should be particularly targeted at, but not limited to, families with a history of features suggestive of SHOX deficiency. Data on the postnatal growth of our index cases is presented which demonstrates that antenatal presentation of SHOX haploinsufficiency is not indicative of severe postnatal growth restriction. Early identification of SHOX deficiency will enable accurate genetic counselling reflecting a good postnatal outcome and facilitate optimal initiation of growth hormone therapy.

Melanocortin receptor accessory proteins in adrenal disease and obesity.

Melanocortin receptor accessory proteins (MRAPs) are regulators of the melanocortin receptor family. MRAP is an essential accessory factor for the functional expression of the MC2R/ACTH receptor. The importance of MRAP in adrenal gland physiology is demonstrated by the clinical condition familial glucocorticoid deficiency type 2. The role of its paralog melanocortin-2-receptor accessory protein 2 (MRAP2), which is predominantly expressed in the hypothalamus including the paraventricular nucleus, has recently been linked to mammalian obesity. Whole body deletion and targeted brain specific deletion of the Mrap2 gene result in severe obesity in mice. Interestingly, Mrap2 complete knockout (KO) mice have increased body weight without detectable changes to food intake or energy expenditure. Rare heterozygous variants of MRAP2 have been found in humans with severe, early-onset obesity. In vitro data have shown that Mrap2 interaction with the melanocortin-4-receptor (Mc4r) affects receptor signaling. However, the mechanism by which Mrap2 regulates body weight in vivo is not fully understood and differences between the phenotypes of Mrap2 and Mc4r KO mice may point toward Mc4r independent mechanisms.

The melanocortin receptors and their accessory proteins.

The five melanocortin receptors (MCRs) named MC1R-MC5R have diverse physiological roles encompassing pigmentation, steroidogenesis, energy homeostasis and feeding behavior as well as exocrine function. Since their identification almost 20 years ago much has been learnt about these receptors. As well as interacting with their endogenous ligands the melanocortin peptides, there is now a growing list of important peptides that can modulate the way these receptors signal, acting as agonists, antagonists, and inverse agonists. The discovery of melanocortin 2 receptor accessory proteins as a novel accessory factor to the MCRs provides further insight into the regulation of these important G protein-coupled receptor.

Loss-of-function mutations in SIM1 contribute to obesity and Prader-Willi-like features.

Sim1 haploinsufficiency in mice induces hyperphagic obesity and developmental abnormalities of the brain. In humans, abnormalities in chromosome 6q16, a region that includes SIM1, were reported in obese children with a Prader-Willi-like syndrome; however, SIM1 involvement in obesity has never been conclusively demonstrated. Here, SIM1 was sequenced in 44 children with Prader-Willi-like syndrome features, 198 children with severe early-onset obesity, 568 morbidly obese adults, and 383 controls. We identified 4 rare variants (p.I128T, p.Q152E, p.R581G, and p.T714A) in 4 children with Prader-Willi-like syndrome features (including severe obesity) and 4 other rare variants (p.T46R, p.E62K, p.H323Y, and p.D740H) in 7 morbidly obese adults. By assessing the carriers' relatives, we found a significant contribution of SIM1 rare variants to intra-family risk for obesity. We then assessed functional effects of the 8 substitutions on SIM1 transcriptional activities in stable cell lines using luciferase gene reporter assays. Three mutations showed strong loss-of-function effects (p.T46R, p.H323Y, and p.T714A) and were associated with high intra-family risk for obesity, while the variants with mild or no effects on SIM1 activity were not associated with obesity within families. Our genetic and functional studies demonstrate a firm link between SIM1 loss of function and severe obesity associated with, or independent of, Prader-Willi-like features.

Rare variants in single-minded 1 (SIM1) are associated with severe obesity.

Single-minded 1 (SIM1) is a basic helix-loop-helix transcription factor involved in the development and function of the paraventricular nucleus of the hypothalamus. Obesity has been reported in Sim1 haploinsufficient mice and in a patient with a balanced translocation disrupting SIM1. We sequenced the coding region of SIM1 in 2,100 patients with severe, early onset obesity and in 1,680 controls. Thirteen different heterozygous variants in SIM1 were identified in 28 unrelated severely obese patients. Nine of the 13 variants significantly reduced the ability of SIM1 to activate a SIM1-responsive reporter gene when studied in stably transfected cells coexpressing the heterodimeric partners of SIM1 (ARNT or ARNT2). SIM1 variants with reduced activity cosegregated with obesity in extended family studies with variable penetrance. We studied the phenotype of patients carrying variants that exhibited reduced activity in vitro. Variant carriers exhibited increased ad libitum food intake at a test meal, normal basal metabolic rate, and evidence of autonomic dysfunction. Eleven of the 13 probands had evidence of a neurobehavioral phenotype. The phenotypic similarities between patients with SIM1 deficiency and melanocortin 4 receptor (MC4R) deficiency suggest that some of the effects of SIM1 deficiency on energy homeostasis are mediated by altered melanocortin signaling.

Loss of function of the melanocortin 2 receptor accessory protein 2 is associated with mammalian obesity.

Melanocortin receptor accessory proteins (MRAPs) modulate signaling of melanocortin receptors in vitro. To investigate the physiological role of brain-expressed melanocortin 2 receptor accessory protein 2 (MRAP2), we characterized mice with whole-body and brain-specific targeted deletion of Mrap2, both of which develop severe obesity at a young age. Mrap2 interacts directly with melanocortin 4 receptor (Mc4r), a protein previously implicated in mammalian obesity, and it enhances Mc4r-mediated generation of the second messenger cyclic adenosine monophosphate, suggesting that alterations in Mc4r signaling may be one mechanism underlying the association between Mrap2 disruption and obesity. In a study of humans with severe, early-onset obesity, we found four rare, potentially pathogenic genetic variants in MRAP2, suggesting that the gene may also contribute to body weight regulation in humans.

Genetic approaches to understanding human obesity.

Obesity and its associated comorbidities represent one of the biggest public health challenges facing the world today. The heritability of body weight is high, and genetic variation plays a major role in determining the interindividual differences in susceptibility or resistance to the obesogenic environment. Here we discuss how genetic studies in humans have contributed to our understanding of the central pathways that govern energy homeostasis. We discuss how the arrival of technological advances such as next-generation sequencing will result in a major acceleration in the pace of gene discovery. The study of patients harboring these genetic variants has informed our understanding of the molecular and physiological pathways involved in energy homeostasis. We anticipate that future studies will provide the framework for the development of a more rational targeted approach to the prevention and treatment of genetically susceptible individuals.