Enhanced MAPK1 Function Causes a Neurodevelopmental Disorder within the RASopathy Clinical Spectrum.

Signal transduction through the RAF-MEK-ERK pathway, the first described mitogen-associated protein kinase (MAPK) cascade, mediates multiple cellular processes and participates in early and late developmental programs. Aberrant signaling through this cascade contributes to oncogenesis and underlies the RASopathies, a family of cancer-prone disorders. Here, we report that de novo missense variants in MAPK1, encoding the mitogen-activated protein kinase 1 (i.e., extracellular signal-regulated protein kinase 2, ERK2), cause a neurodevelopmental disease within the RASopathy phenotypic spectrum, reminiscent of Noonan syndrome in some subjects. Pathogenic variants promote increased phosphorylation of the kinase, which enhances translocation to the nucleus and boosts MAPK signaling in vitro and in vivo. Two variant classes are identified, one of which directly disrupts binding to MKP3, a dual-specificity protein phosphatase negatively regulating ERK function. Importantly, signal dysregulation driven by pathogenic MAPK1 variants is stimulus reliant and retains dependence on MEK activity. Our data support a model in which the identified pathogenic variants operate with counteracting effects on MAPK1 function by differentially impacting the ability of the kinase to interact with regulators and substrates, which likely explains the minor role of these variants as driver events contributing to oncogenesis. After nearly 20 years from the discovery of the first gene implicated in Noonan syndrome, PTPN11, the last tier of the MAPK cascade joins the group of genes mutated in RASopathies.

Endocrinological manifestations in RASopathies.

The evaluation of endocrine involvement in RASopathies is important for the care and follow-up of patients affected by these conditions. Short stature is a cardinal feature of RASopathies and correlates with multiple factors. Growth hormone treatment is a therapeutic possibility to improve height and quality of life. Assessment of growth rate and growth laboratory parameters is routine, but age at start of therapy, dose and effects of growth hormone on final height need to be clarified. Puberty disorders and gonadal dysfunction, in particular in males, are other endocrinological areas to evaluate for their effects on growth and development. Thyroid dysfunction, autoimmune disease and bone involvement have also been reported in RASopathies. In this brief review, we describe the current knowledge on growth, growth hormone therapy, endocrinological involvement in patients affected by RASopathies.

From Whole Gene Deletion to Point Mutations of EP300-Positive Rubinstein-Taybi Patients: New Insights into the Mutational Spectrum and Peculiar Clinical Hallmarks.

Rubinstein-Taybi syndrome (RSTS) is a rare congenital neurodevelopmental disorder characterized by growth deficiency, skeletal abnormalities, dysmorphic features, and intellectual disability. Causative mutations in CREBBP and EP300 genes have been identified in ∼55% and ∼8% of affected individuals. To date, only 28 EP300 alterations in 29 RSTS clinically described patients have been reported. EP300 analysis of 22 CREBBP-negative RSTS patients from our cohort led us to identify six novel mutations: a 376-kb deletion depleting EP300 gene; an exons 17-19 deletion (c.(3141+1_3142-1)_(3590+1_3591-1)del/p.(Ile1047Serfs*30)); two stop mutations, (c.3829A>T/p.(Lys1277*) and c.4585C>T/p.(Arg1529*)); a splicing mutation (c.1878-12A>G/p.(Ala627Glnfs*11)), and a duplication (c.4640dupA/p.(Asn1547Lysfs*3)). All EP300-mutated individuals show a mild RSTS phenotype and peculiar findings including maternal gestosis, skin manifestation, especially nevi or keloids, back malformations, and a behavior predisposing to anxiety. Furthermore, the patient carrying the complete EP300 deletion does not show a markedly severe clinical picture, even if a more composite phenotype was noticed. By characterizing six novel EP300-mutated patients, this study provides further insights into the EP300-specific clinical presentation and expands the mutational repertoire including the first case of a whole gene deletion. These new data will enhance EP300-mutated cases identification highlighting distinctive features and will improve the clinical practice allowing a better genotype-phenotype correlation.

Response to long-term growth hormone therapy in patients affected by RASopathies and growth hormone deficiency: Patterns of growth, puberty and final height data.

RASopathies are developmental disorders caused by heterozygous germline mutations in genes encoding proteins in the RAS-MAPK signaling pathway. Reduced growth is a common feature. Several studies generated data on growth, final height (FH), and height velocity (HV) after growth hormone (GH) treatment in patients with these disorders, particularly in Noonan syndrome, the most common RASopathy. These studies, however, refer to heterogeneous cohorts in terms of molecular information, GH status, age at start and length of therapy, and GH dosage. This work reports growth data in 88 patients affected by RASopathies with molecularly confirmed diagnosis, together with statistics on body proportions, pubertal pattern, and FH in 33, including 16 treated with GH therapy for proven GH deficiency. Thirty-three patients showed GH deficiency after pharmacological tests, and were GH-treated for an average period of 6.8 ± 4.8 years. Before starting therapy, HV was -2.6 ± 1.3 SDS, and mean basal IGF1 levels were -2.0 ± 1.1 SDS. Long-term GH therapy, starting early during childhood, resulted in a positive height response compared with untreated patients (1.3 SDS in terms of height-gain), normalizing FH for Ranke standards but not for general population and Target Height. Pubertal timing negatively affected pubertal growth spurt and FH, with IGF1 standardized score increased from -2.43 to -0.27 SDS. During GH treatment, no significant change in bone age velocity, body proportions, or cardiovascular function was observed.

GH Therapy and first final height data in Noonan-like syndrome with loose anagen hair (Mazzanti syndrome).

Noonan-like syndrome with loose anagen hair (NS/LAH or Mazzanti Syndrome) is caused by a single missense mutation in SHOC2 promoting tN-myristoylation of the encoded protein. Cardinal features include facial features resembling NS, short stature often associated with proven growth hormone deficiency (GHD), typical ectodermal anomalies, and distinctive behavior. Overall, the clinical features are more severe than those generally observed in NS, even though the phenotype improves with age. We report on growth and pubertal trend in seven patients heterozygous for a mutated SHOC2 allele, treated with long-term GH-therapy, and final height (FH) in three of them. They were approximately -3 SDS below the Italian general population standards, they had very low IGF1 levels at baseline and GHD at pharmacological tests. All patients were treated with GH (0.035 mg/kg/day) for a mean period of 8.49 ± 5.72 years. After the 1st year of GH-therapy, IGF1 level and height velocity had increased. Three of 7 patients reached the FH (-2.34 ± 0.12 SDS) at 18.25 ± 0.73 years, after GH administration for 12.39 ± 2.12 years. Pubertal development was variable, showing a prolonged and delayed puberty or rapid pubertal progression that could impair the FH. Overall, our data in this small cohort suggest that NS/LAH patients benefit from long-term GH-therapy, although they do not show the characteristic catch-up growth of isolated GHD. While the observed growth and pubertal behavior is consistent with a dysfunction of the hypothalamic-pituitary-gonadal axis, the functional link between SHOC2 and the GH/IGF signaling pathways remains to be clarified.

Lipid profile in Noonan syndrome and related disorders: trend by age, sex and genotype.

Background: RASopathies are developmental disorders caused by dysregulation of the RAS-MAPK signalling pathway, which contributes to the modulation of multiple extracellular signals, including hormones and growth factors regulating energetic metabolism, including lipid synthesis, storage, and degradation. Subjects and methods: We evaluated the body composition and lipid profiles of a single-centre cohort of 93 patients with a molecularly confirmed diagnosis of RASopathy by assessing height, BMI, and total cholesterol, HDL, triglycerides, apolipoprotein, fasting glucose, and insulin levels, in the context of a cross sectional and longitudinal study. We specifically investigated and compared anthropometric and haematochemistry data between the Noonan syndrome (NS) and Mazzanti syndrome (NS/LAH) groups. Results: At the first evaluation (9.5 ± 6.2 years), reduced growth (-1.80 ± 1.07 DS) was associated with a slightly reduced BMI (-0.34 DS ± 1.15 DS). Lipid profiling documented low total cholesterol levels (< 5th percentile) in 42.2% of the NS group; in particular, in 48.9% of PTPN11 patients and in 28.6% of NS/LAH patients compared to the general population, with a significant difference between males and females. A high proportion of patients had HDL levels lower than the 26th percentile, when compared to the age- and sex-matched general population. Triglycerides showed an increasing trend with age only in NS females. Genotype-phenotype correlations were also evident, with particularly reduced total cholesterol in about 50% of patients with PTPN11 mutations with LDL-C and HDL-C tending to decrease during puberty. Similarly, apolipoprotein A1 and apolipoprotein B deficits were documented, with differences in prevalence associated with the genotype for apolipoprotein A1. Fasting glucose levels and HOMA-IR were within the normal range. Conclusion: The present findings document an unfavourable lipid profile in subjects with NS, in particular PTPN11 mutated patients, and NS/LAH. Further studies are required to delineate the dysregulation of lipid metabolism in RASopathies more systematically and confirm the occurrence of previously unappreciated genotype-phenotype correlations involving the metabolic profile of these disorders.

Turner syndrome strategies to improve care outcomes--cardiac evaluation using new imaging techniques.

Turner syndrome (TS) is at high risk for congenital heart diseases (CHD), aortic dilatation (AoDil) and dissection. New imaging techniques such as MRI have revealed the presence of vascular anomalies (VA) undetected at echo. MR angiography has shown a high prevalence of aortic and venous anomalies. The VA often coexist and interact to increase the risk of premature death in adulthood. AoDil and VA have been found also in asymptomatic individuals with no predisposing factors, but the prevalence is still unknown. We evaluated 100 TS subjects (15-35 yrs) with no aortic CHD at echocardiography with transthoracic MRA; 42 of them showed VA and 58 did not. Aortic diameters were indexed on BSA. At the sinuses of Valsalva a higher prevalence of AoDil was found in subjects with VA than without; 57% of them showed AoDil. The presence of VA (elongation of the transverse arch, bovine arch, left superior vena cava, PAPVD etc.) increased their relative risk of AoDil by more than 2 times. Excluding BSA influence, a severe phenotype influenced positively ascending AoDil. New imaging techniques enhance our ability to provide a prognosis for their adult age and in particular before they seek to become pregnant.

Developmental syndromes: growth hormone deficiency and treatment.

Developmental syndromes are characterized by numerous phenotypical signs and malformations. In most of them such as Turner, Noonan, Prader-Willi, Silver-Russel, Williams, Kabuki, Leri-Weill syndrome and skeletal dysplasias, short stature is a common feature. Growth defect is very often related to a defect in cellular growth, but some unknown abnormality in GH action is possible. Recently, the greater availability of recombinant GH has expanded the interest towards GH secretion and therapy also in developmental syndromes. We recognize syndromes associated with GH deficiency (GHD), showing a developmental midline defect such as Pallister-Hall syndrome, septo-optic dysplasia, but many of these conditions do not have a convincing link with GHD. Moreover, some conditions, in particular the well-studied Turner syndrome, that do not have a real GHD, have proven to benefit from GH therapy at supra-physiological doses obtaining a higher final height than the expected one according to the natural history. This has expanded the indications for GH therapy. The aim of our paper is to review the literature on GH secretion, on the effects and costs-benefits of GH therapy in many dysmorphic syndromes, presenting some results of GH secretion and therapy obtained in our experience.

Correlations of phenotype and genotype in relation to morphologic remodelling of the aortic root in patients with Turner's syndrome.

BACKGROUND: Patients with Turner's syndrome are at risk of aortic dilation and dissection. Currently, it is not known whether such dilation is related to associated cardiovascular abnormalities, or to the genetic anomaly itself. METHODS: We studied echocardiographically 107 patients with genetically proven Turner's syndrome, with heterogeneous underlying karyotypes, and without associated cardiac lesions. Their average age was 19.6 plus or minus 8.4 years. We compared the finding with those from 71 age-matched healthy female volunteers. The diameter of the aorta was measured at the level of the basal attachments of the aortic valvar leaflets, the sinuses of Valsalva, the sinutubular junction, and its ascending component. RESULTS: Compared to control subjects, the patients with Turner's syndrome had larger diameters of the aorta at the level of the sinuses of Valsalva, at 23.4+/-4.8 versus 25.5+/-4.1 millimetres (p = 0.0014), the sinutubular junction, at 19.9+/-3.8 versus 23.3+/-4.1 millimetres (p < 0.0001), and the ascending aorta, at 22.3+/-4.9 versus 24.6+/-4.4 millimetres (p = 0.0011). Dilation of the sinutubular junction, found in just over one-quarter of the patients, was more common than dilation of the ascending aorta, the latter found in less than one-tenth. The patients with Turner's syndrome, therefore, presented with remodelling of the aortic root, with relative dilation of the sinutubular junction. The underlying karyotype influenced both the dimensions of the sinutubular junction (p = 0.0054), and the ascending aorta (p = 0.0064), so that patients with the karyotype 45X had larger aortas. The karyotype was the strongest predictor by multivariate analysis for dilation at both these sites (p = 0.0138 and 0.0085, respectively). CONCLUSIONS: Dilation at the sinutubular junction is frequent in patients with Turner's syndrome, and is more common than dilation of the ascending aorta. The syndrome is associated with a remodelling of the aortic root, with prominent dilation of the sinutubular junction. There seems to be a relation between aortic dilation and the underlying genotype.

Novel Mutations and Unreported Clinical Features in KBG Syndrome.

KBG syndrome is an autosomal dominant disorder caused by pathogenic variants within ANKRD11 or deletions of 16q24.3 which include ANKRD11. It is characterized by distinctive facial features, developmental delay, short stature, and skeletal anomalies. We report 12 unrelated patients where a clinical diagnosis of KBG was suspected and confirmed by targeted analyses. Nine patients showed a point mutation in ANKRD11 (none of which were previously reported) and 3 carried a 16q24.3 deletion. All patients presented with typical facial features and macrodontia. Skeletal abnormalities were constant, and the majority of patients showed joint stiffness. Three patients required growth hormone treatment with a significant increase of height velocity. Brain malformations were identified in 8 patients. All patients showed behavioral abnormalities and most had developmental delay. Two patients had hematological abnormalities. We emphasize that genetic analysis of ANKRD11 can easily reach a detection rate higher than 50% thanks to clinical phenotyping, although it is known that a subset of ANKRD11-mutated patients show very mild features and will be more easily identified through the implementation of gene panels or exome sequencing. Joint stiffness was reported previously in few patients, but it seems to be a common feature and can be helpful for the diagnosis. Hematological abnormalities could be present and warrant a specific follow-up.

Challenges in the clinical interpretation of small de novo copy number variants in neurodevelopmental disorders.

In clinical genetics, the need to discriminate between benign and pathogenic variants identified in patients with neurodevelopmental disorders is an absolute necessity. Copy number variants (CNVs) of small size can enable the identification of genes that are critical for neurologic development. However, assigning a definite association with a specific disorder is a difficult task. Among 328 trios analyzed over seven years of activity in a single laboratory, we identified 19 unrelated patients (5.8%) who carried a small (<500 kb) de novo CNV. Four patients had an additional independent de novo CNV. Nine had a variant that could be assigned as definitely pathogenic, whereas the remaining CNVs were considered as variants of unknown significance (VUS). We report clinical and molecular findings of patients harboring VUS. We reviewed the medical literature available for genes impacted by CNVs, obtained the probability of truncating loss-of-function intolerance, and compared overlapping CNVs reported in databases. The classification of small non-recurrent CNVs remains difficult but, among our findings, we provide support for a role of SND1 in the susceptibility of autism, describe a new case of the rare 17p13.1 microduplication syndrome, and report an X-linked duplication involving KIF4A and DLG3 as a likely cause of epilepsy.

The Influence of GH Treatment on Glucose Homeostasis in Girls With Turner Syndrome: A 7-Year Study.

CONTEXT: Growth hormone (GH) influences glucose homeostasis mainly by negatively affecting insulin sensitivity. OBJECTIVE: To longitudinally study insulin sensitivity [via homeostasis model assessment of insulin sensitivity (HOMA-S)], insulin secretion [insulinogenic index (IGI)], and capacity of ß cells to adapt to changes in insulin sensitivity [oral disposition index (ODI)] in girls with Turner syndrome (TS) undergoing GH treatment. DESIGN AND SETTING: Longitudinal, retrospective, 7-year study conducted in a tertiary pediatric endocrine unit and university pediatric clinic. PATIENTS AND METHODS: We studied 104 patients with TS (mean age ± standard deviation, 9.1 ± 3.4 years) for a median of 7.2 years. INTERVENTION: Every year, the children underwent an oral glucose tolerance test, which was used to calculate HOMA-S, IGI, and ODI. RESULTS: HOMA-S, IGI, and ODI did not significantly change. CONCLUSION: The results are reassuring, showing no negative influence of GH treatment on insulin sensitivity and on ß-cell secretory capacity in girls with TS.

Neuropsychiatric phenotype in a child with pseudohypoparathyroidism.

Pseudohypoparathyroidism (PHP) is a rare heterogeneous genetic disease characterized by end-organ resistance to parathyroid hormone. In adulthood, heterogeneous neurological and psychiatric disorders have been reported which are associated with hypoparathyroidism in general and with PHP in particular, while for childhood, data are scanty. We report a case of a boy with PHP type 1b, in whom neurological signs at the onset prevailed, characterized by tic-like dyskinesias associated with a series of heterogeneous not well-defined neurological and behavioral features, describing the diagnostic work-up performed and the follow-up. We suggest that the diagnostic hypothesis of PHP might be considered when dealing with a child with tic-like dyskinesias, especially if associated with a series of heterogeneous not well-defined neurological and behavioral features. In these cases, treatment with calcitriol and calcium has to be started as soon as possible to achieve a prompt and persistent clinical improvement.

The Influence of Growth Hormone Treatment on Glucose Homeostasis in GrowthHormone-Deficient Children: A Six-Year Follow-Up Study.

BACKGROUND: Growth hormone (GH) influences glucose homeostasis by negatively affecting insulin sensitivity, leading to a compensatory increase in insulin secretion. It has recently been reported, in animals and humans, that GH might also stimulate insulin secretion by directly affecting the growth and function of pancreatic ß-cells. The aim of this work was to longitudinally study the insulin sensitivity (HOMA-S), insulin secretion [insulinogenic index (IGI)] and capacity of ß-cells to adapt to changes in insulin sensitivity [oral disposition index (ODI)] in GH-deficient (GHD) children under GH treatment. METHODS: We studied 99 GHD (62 male, 37 female; age 8.9 ± 3.5 years) children for a median period of 6 years (range 1.5-16.2). Every year, our patients underwent an oral glucose tolerance test, which was used to calculate the HOMA-S, IGI and ODI. RESULTS: Although HOMA-S remained unchanged, an increase in IGI and ODI was observed, becoming significant after 6 years of treatment (1.25 ± 1.28 vs. 2.35 ± 2.38, p < 0.05 and 0.57 ± 0.68 vs. 1.50 ± 1.92, p < 0.01, respectively). CONCLUSION: Our results suggest a positive influence of GH treatment on the ß-cell secretory capacity in children with GH deficiency. © 2016 S. Karger AG, Basel.

Loss-of-function variants of SETD5 cause intellectual disability and the core phenotype of microdeletion 3p25.3 syndrome.

Intellectual disability (ID) has an estimated prevalence of 2-3%. Due to its extreme heterogeneity, the genetic basis of ID remains elusive in many cases. Recently, whole exome sequencing (WES) studies revealed that a large proportion of sporadic cases are caused by de novo gene variants. To identify further genes involved in ID, we performed WES in 250 patients with unexplained ID and their unaffected parents and included exomes of 51 previously sequenced child-parents trios in the analysis. Exome analysis revealed de novo intragenic variants in SET domain-containing 5 (SETD5) in two patients. One patient carried a nonsense variant, and the other an 81 bp deletion located across a splice-donor site. Chromosomal microarray diagnostics further identified four de novo non-recurrent microdeletions encompassing SETD5. CRISPR/Cas9 mutation modelling of the two intragenic variants demonstrated nonsense-mediated decay of the resulting transcripts, pointing to a loss-of-function (LoF) and haploinsufficiency as the common disease-causing mechanism of intragenic SETD5 sequence variants and SETD5-containing microdeletions. In silico domain prediction of SETD5, a predicted SET domain-containing histone methyltransferase (HMT), substantiated the presence of a SET domain and identified a novel putative PHD domain, strengthening a functional link to well-known histone-modifying ID genes. All six patients presented with ID and certain facial dysmorphisms, suggesting that SETD5 sequence variants contribute substantially to the microdeletion 3p25.3 phenotype. The present report of two SETD5 LoF variants in 301 patients demonstrates a prevalence of 0.7% and thus SETD5 variants as a relatively frequent cause of ID.