Jean-Claude Carel

Loss-of-function mutations in FGFR1 cause autosomal dominant Kallmann syndrome

We took advantage of overlapping interstitial deletions at chromosome 8p11–p12 in two individuals with contiguous gene syndromes and defined an interval of roughly 540 kb associated with a dominant form of Kallmann syndrome, KAL2. We establish here that loss-of-function mutations in FGFR1 underlie KAL2 whereas a gain-of-function mutation in FGFR1 has been shown to cause a form of craniosynostosis. Moreover, we suggest that the KAL1 gene product, the extracellular matrix protein anosmin-1, is involved in FGF signaling and propose that the gender difference in anosmin-1 dosage (because KAL1 partially escapes X inactivation) explains the higher prevalence of the disease in males.

Child Health, Developmental Plasticity, and Epigenetic Programming

Plasticity in developmental programming has evolved in order to provide the best chances of survival and reproductive success to the organism under changing environments. Environmental conditions that are experienced in early life can profoundly influence human biology and long-term health. Developmental origins of health and disease and life-history transitions are purported to use placental, nutritional, and endocrine cues for setting long-term biological, mental, and behavioral strategies in response to local ecological and/or social conditions. The window of developmental plasticity extends from preconception to early childhood and involves epigenetic responses to environmental changes, which exert their effects during life-history phase transitions. These epigenetic responses influence development, cell- and tissue-specific gene expression, and sexual dimorphism, and, in exceptional cases, could be transmitted transgenerationally. Translational epigenetic research in child health is a reiterative process that ranges from research in the basic sciences, preclinical research, and pediatric clinical research. Identifying the epigenetic consequences of fetal programming creates potential applications in clinical practice: the development of epigenetic biomarkers for early diagnosis of disease, the ability to identify susceptible individuals at risk for adult diseases, and the development of novel preventive and curative measures that are based on diet and/or novel epigenetic drugs.

Long-term mortality and causes of death in isolated GHD, ISS, and SGA patients treated with recombinant growth hormone during childhood in Belgium, The Netherlands, and Sweden: preliminary report of 3 countries participating in the EU SAGhE study

CONTEXTnThe long-term mortality in adults treated with recombinant GH during childhood has been poorly investigated. Recently released data from the French part of the European Union Safety and Appropriateness of GH treatments in Europe (EU SAGhE) study have raised concerns on the long-term safety of GH treatment.nnnOBJECTIVEnTo report preliminary data on long-term vital status and causes of death in patients with isolated GH deficiency or idiopathic short stature or born small for gestational age treated with GH during childhood, in Belgium, The Netherlands, and Sweden.nnnDESIGNnData were retrieved from national registries of GH-treated patients and vital status from National Population Registries. Causes of death were retrieved from a National Cause of Death Register (Sweden), Federal and Regional Death Registries (Belgium), or individual patient records (The Netherlands).nnnPATIENTSnAll patients diagnosed with isolated GH deficiency or idiopathic short stature or born small for gestational age started on recombinant GH during childhood from 1985-1997 and who had attained 18 yr of age by the end of 2010 were included. Vital status was available for approximately 98% of these 2,543 patients, corresponding to 46,556 person-years of observation.nnnMAIN OUTCOME MEASUREnVital status, causes of death, age at death, year of death, duration of GH treatment, and mean GH dose during treatment were assessed.nnnRESULTSnAmong 21 deaths identified, 12 were due to accidents, four were suicides, and one patient each died from pneumonia, endocrine dysfunction, primary cardiomyopathy, deficiency of humoral immunity, and coagulation defect.nnnCONCLUSIONSnIn these cohorts, the majority of deaths (76%) were caused by accidents or suicides. Importantly, none of the patients died from cancer or from a cardiovascular disease.

T-Cell Response to Proinsulin and Insulin in Type 1 and Pretype 1 Diabetes

Insulin-dependent diabetes mellitus (IDDM) results from the selective destruction of pancreatic β cells by a T cell-mediated autoimmune process. Insulin and proinsulin are the only known β cell-specific autoantigens. Using short-term cultures of freshly isolated peripheral blood mononuclear cells, we evaluated T-cell responses to proinsulin and to insulin in IDDM patients and individuals at risk for IDDM. A proliferative T-cell response to proinsulin was observed in only 2 of 26 recent-onset IDDM subjects and 2 of 12 long-standing IDDM subjects and was associated with a proliferative response to insulin. In contrast, 5 of 13 islet cell autoantibody-positive first-degree relatives of IDDM patients showed a proliferative response to proinsulin alone, 3 of 13 to insulin alone, and 1 of 13 to both insulin and proinsulin. Overall, 9 of 13 ICA-positive first-degree relatives responded to either proinsulin or insulin. We observed an inverse relationship between antiinsulin antibodies and T-cell responses to insulin in ICA-positive first-degree relatives but not in long-standing IDDM patients. Our data indicate that proinsulin is a major antigen in IDDM and, further, illustrate the difference between the autoimmune response to insulin and the immune response to exogenous insulin.

Safety of Recombinant Human Growth Hormone

With an increasing spectrum of indications for growth hormone (GH), knowledge of the short- and long-term safety of this treatment is essential. In this chapter we review the main adverse effects that have been demonstrated or discussed after long-term GH treatment in children. It is well recognized that plasma insulin concentrations increase during GH treatment. The incidence of type 2 diabetes is raised during GH treatment, especially in subjects with other risk factors. Recommendations include assessing glucose tolerance by measuring plasma glucose and HbA1c before and during treatment. There is no consensus on the indications for insulin measurement and/or oral glucose tolerance tests. Other recognized short-term complications of GH treatment include pseudo-tumour cerebri, otitis media (Turner syndrome), and orthopaedic problems such as worsening of scoliosis and slipped femoral epiphysis. There are reports of sudden death within the first 6 months of treatment in children with Prader-Willi syndrome, mostly associated with severe obesity. Large cohort follow-up studies suggest that children treated with GH following childhood cancer treatment do not have a greater number of relapses, but there may be a higher incidence of second primary tumours in the early years of GH therapy. A cohort treated with human pituitary GH showed a higher incidence of tumours, and a GH effect on tumorigenesis has been seen in follow-up studies of acromegaly raising the question of whether de novo cancer risk may be increased. A new prospective pan-European safety surveillance study (SAGhE) has been launched to address these essential questions. The role of monitoring the IGF-1 response (total or free concentrations) to GH treatment to predict long-term safety is unclear at present. Attempts to target IGF-1 levels within the normal range may result in the use of excessive doses of GH. In general, higher dosage GH regimens may be associated with supraphysiological IGF-1 levels.

Expression of Preproinsulin-2 Gene Shapes the Immune Response to Preproinsulin in Normal Mice

Deciphering mechanisms involved in failure of self tolerance to preproinsulin-2 is a key issue in type 1 diabetes. We used nonautoimmune 129SV/Pas mice lacking preproinsulin-2 to study the immune response to preproinsulin-2. In these mice, a T cell response was detected after immunization with several preproinsulin-2 peptides and confirmed by generating hybridomas. Activation of some of these hybridomas by wild-type (wt) islet cells or recombinant murine proinsulin-2 demonstrated that two epitopes can be generated from the naturally expressed protein. Although T cells from wt mice responded to preproinsulin-2 peptides, we could not detect a response to the naturally processed epitopes in these mice. Moreover, after immunization with recombinant whole proinsulin-2, a T cell response was detected in preproinsulin-2-deficient but not in wt mice. This suggests that islet preproinsulin-2-autoreactive T cells are functionally eliminated in wt mice. We used a transplantation model to evaluate the relevance of reactivity to preproinsulin-2 in vivo. Wild-type preproinsulin-2-expressing islets transplanted in preproinsulin-2-deficient mice elicited a mononuclear cell infiltration and insulin Abs. Graft infiltration was further increased by immunization with preproinsulin-2 peptides. Preproinsulin-2 expression thus shapes the immune response and prevents self reactivity to the islet. Moreover, islet preproinsulin-2 primes an immune response to preproinsulin-2 in deficient mice.

Phenotypic Homogeneity and Genotypic Variability in a Large Series of Congenital Isolated ACTH-Deficiency Patients with TPIT Gene Mutations

CONTEXTnCongenital isolated ACTH deficiency (IAD) is a rare disease characterized by low plasma ACTH and cortisol levels and preservation of all other pituitary hormones. This condition was poorly defined before we identified TPIT, a T-box transcription factor with a specific role in differentiation of the corticotroph lineage in mice and humans, as its principal molecular cause.nnnOBJECTIVEnWe have enlarged our series of IAD patients to better characterize the phenotype and the genotype of this rare disease.nnnDESIGNnEach exon of the TPIT gene was amplified and sequenced in IAD patients without any identified cause. A functional analysis of each new TPIT mutation was performed.nnnRESULTSnWe described the largest series of 91 IAD patients and identified three distinct groups: neonatal onset complete or partial IAD or late onset IAD. We did not identify any TPIT mutation in patients with partial or late-onset IAD. However, we found a TPIT mutation in 65% of patients with neonatal-onset complete IAD. These patients are homozygous or compound heterozygous for TPIT mutations, and their parents are healthy heterozygous carriers. We identified nine new mutations: four missense, one one-nucleotide deletion, three splice-site mutations, and one large deletion. TPIT mutations lead to loss of function by different mechanisms, such as non-sense-mediated mRNA decay, abnormal mRNA splicing, loss of TPIT DNA binding or protein-protein interaction defects.nnnCONCLUSIONnTPIT mutations are responsible for two thirds of neonatal-onset complete IAD but can not be detected in partial or late-onset IAD.

Treatment of Children Born Short for Gestational Age: A European Perspective

The use of growth hormone (GH) has progressively moved from a substitution therapy to a pharmacological agent promoting growth when it is otherwise considered insufficient. This process has progressed stepwise from conditions with definite diagnoses such as Turner syndrome towards children born small for gestational age (SGA) and more recently those with idiopathic short stature. Unsurprisingly, no set European or national perspective can be presented given the multiple points of view that must be taken into account when considering these treatments. In France, the use of GH has been approved for use in SGA children since 1995 and has been covered by the national insurance system since 1997. National data regarding the use of GH for this indication will be presented, in particular with regard to the recommendations for use made by the national insurance system. In 2003, after a complex procedure lasting more than 2 years, two GH preparations, including Norditropin®, were approved at European level for use in SGA children. Based on the data presented, the European Medicines Evaluation Agency approved a dose of 35 µg/kg per day, which is that generally used in GH deficiency. This is paradoxical, given that GH-deficient children are generally considered to be more sensitive to treatment than their non-GH-deficient counterparts. It is of interest that the influence of GH dose on outcome has only been demonstrated in the first years of treatment and not in any long-term, near-adult-height analyses. Thus the ‘European perspective’ emphasizes long-term results rather than short-term catch-up. By contrast, in the USA a higher dose is recommended, emphasizing on short-term gain. Other differences concern the minimum age at the start of treatment and the minimum height deficit before chronic treatment can be instituted.

Haploinsufficiency of Dmxl2, Encoding a Synaptic Protein, Causes Infertility Associated with a Loss of GnRH Neurons in Mouse

Rabconnectin-3α and the control of puberty Human genetics shows that low levels of rabconnectin-3α cause a loss of the neurons that produce gonadotropin-releasing hormone, revealing a new mechanism for incomplete puberty and infertility.

Optimal use of growth hormone therapy for maximizing adult height in children born small for gestational age

Growth retardation is a well-known complication of being born small for gestational age (SGA). Approximately 10% of children born SGA do not experience postnatal catch-up growth and are at risk for short adult height. The use of growth hormone (GH) therapy in these short children appears to increase their adult height, but modalities of GH administration remain controversial. Numerous therapeutic strategies have been developed to optimize the efficacy of GH treatment. Data concerning the influence of age at start of GH treatment, duration of GH treatment, GH dosage and method of GH administration on height gain and adult height are reported in this chapter. Longitudinal studies addressing the safety of GH treatment in SGA children are reassuring, but long-term follow-up remains necessary. Recommendations on the management of SGA children during GH treatment are given.