Acid-labile subunit (ALS) forms ternary complexes with insulin like growth factor-1 (IGF-1) and IGF-binding protein-3 (IGFBP-3) and is essential for normal circulating IGF-1 levels. The
gene encodes ...the ALS and mutations in
cause ALS deficiency. We describe a patient with ALS deficiency with a novel homozygous frameshift mutation in
presenting with short stature and delayed puberty but ultimately achieving an adult height (AH) comparable to his target height (TH). A 15.25 year old boy presented with short stature (149.9 cm, -3.04 standard deviation score). The patient had a low circulating IGF-1 concentration, extremely low IGFBP-3 concentration, insulin resistance and osteopenia. The peak growth hormone (GH) response to GH stimulation test was high (31.6 ng/mL). Sequencing of
revealed a novel, homozygous, frameshift mutation (p.Ser555Thrfs.19). His mother and elder sister were heterozygous carriers. Although he had delayed puberty and short stature at the onset of puberty, he reached his TH and an AH similar to those of his heterozygous mother and sister. The heterozygous carriers had normal or low IGF-1 concentrations and low IGFBP-3 concentrations but not as markedly low as that of the patient. They had normally timed puberty, insulin metabolism and bone mineral density (BMD). The phenotype of ALS deficiency is quite variable. Despite short stature and delayed puberty, patients can achieve normal pubertal growth and AH. ALS deficiency may cause osteopenia and hyperinsulinemia. Heterozygous carriers may have normal prenatal growth, puberty, insulin metabolism and BMD.
Cholesterol side-chain cleavage enzyme (P450scc) deficiency is a rare genetic disorder causing primary adrenal insufficiency with or without a 46,XY disorder of sexual development (DSD). Herein, we ...report a case of the combination of primary adrenal insufficiency, a DSD (testes with female external genitalia in a setting of a 47,XXY karyotype), and Angelman syndrome.
Comprehensive genetic analyses were performed, including a single nucleotide polymorphism microarray and whole-exome sequencing. In vitro studies were performed to evaluate the pathogenicity of the novel mutation that was identified by whole-exome sequencing.
The patient was found to have segmental uniparental disomy (UPD) of chromosome 15 explaining her diagnosis of Angelman syndrome. Whole-exome sequencing further revealed a novel homozygous intronic variant in CYP11A1, the gene encoding P450scc, found within the region of UPD. In vitro studies confirmed that this variant led to decreased efficiency of CYP11A1 splicing.
We report the first case of the combination of 2 rare genetic disorders, Angelman syndrome, and P450scc deficiency. After 20 years of diagnostic efforts, significant advances in genetic diagnostic technology allowed us to determine that these 2 disorders originate from a unified genetic etiology, segmental UPD unmasking a novel recessive mutation in CYP11A1.
Fibroblast growth factors and their receptors (FGFR) have major roles in both human growth and oncogenesis. In adults, therapeutic FGFR inhibitors have been successful against tumors that carry ...somatic FGFR mutations. In pediatric patients, trials testing these anti-tumor FGFR inhibitor therapeutics are underway, with several recent reports suggesting modest positive responses. Herein, we report an unforeseen outcome in a pre-pubescent child with an FGFR1-mutated glioma who was successfully treated with FDA-approved erdafitinib, a pan-FGFR inhibitor approved for treatment of Bladder tumors. While on treatment with erdafitinib, the patient experienced rapid skeletal and long bone overgrowth resulting in kyphoscoliosis, reminiscent of patients with congenital loss-of-function FGFR3 mutations. We utilized normal dermal fibroblast cells established from the patient as a surrogate model to demonstrate that insulin-like growth factor 1 (IGF-1), a factor important for developmental growth of bones and tissues, can activate the PI3K/AKT pathway in erdafitinib-treated cells but not the MAPK/ERK pathway. The IGF-I-activated PI3K/AKT signaling rescued normal fibroblasts from the cytotoxic effects of erdafitinib by promoting cell survival. We, therefore, postulate that IGF-I-activated P13K/AKT signaling likely continues to promote bone elongation in the growing child, but not in adults, treated with therapeutic pan-FGFR inhibitors. Importantly, since activated MAPK signaling counters bone elongation, we further postulate that prolonged blockage of the MAPK pathway with pan-FGFR inhibitors, together with actions of growth-promoting factors including IGF-1, could explain the abnormal skeletal and axial growth suffered by our pre-pubertal patient during systemic therapeutic use of pan-FGFR inhibitors. Further studies to find more targeted, and/or appropriate dosing, of pan-FGFR inhibitor therapeutics for children are essential to avoid unexpected off-target effects as was observed in our young patient.
The myriad actions of growth hormone (GH) are still incompletely understood, despite decades of research. Although it is a major regulator of post-natal growth in mammals, much of its effects on ...skeletal growth are recognized to be mediated indirectly, through the stimulation of production of insulin-like growth factor (IGF)-I, as well as some of the major serum carrier proteins for IGF-I and -II, such as IGF-binding protein-3 (IGFBP-3) and the acid-labile subunit (ALS). The regulation of IGF-I production by GH appears to be mediated entirely by signalling through the Janus kinase (JAK) 2 pathway, via the phosphorylation of the transcription factor, signal transducer and activator of transcription (STAT) 5b. GH also signals, however, through additional pathways that are likely to be critical to the metabolic actions of GH.
STAT5b deficiency: Lessons from STAT5b gene mutations Hwa, Vivian, Ph.D; Nadeau, Kari, M.D., Ph.D; Wit, Jan M., M.D ...
Best Practice & Research Clinical Endocrinology & Metabolism,
02/2011, Letnik:
25, Številka:
1
Journal Article
Recenzirano
Growth hormone (GH) regulates insulin-like growth factor (IGF)-I production primarily through activation of the GH receptor (GHR)-signal transducer and activator of transcription (STAT)-5b signaling ...cascade. One of four STAT proteins (STAT1, −3, −5a and −5b) activated by the GH–GHR system, the critical importance of STAT5b in IGF-I production became evident with the identification of homozygous, autosomal recessive STAT5b mutations in patients who presented with severe postnatal growth failure, growth hormone insensitivity syndrome (GHIS) and marked IGF-I deficiency. Unlike GHIS due to GHR mutations, patients carrying STAT5b mutations also presented with chronic pulmonary disease and evidence of perturbations of T-cell homeostasis. At present, no single treatment(s) is available to improve both poor statural growth and immune deficiency. Continued clinical evaluations of patients with STAT5b mutations and elucidating the impact of the mutation on STAT5b structure and function, are important to understanding the pathophysiology of this rare, complex, disease (MIM 245590).
Context:
IGF-I, essential for normal human growth in utero and postnatally, mediates its effects through the IGF-I receptor (IGF1R). More than nine heterozygous mutations, including one compound ...heterozygous mutation, of the IGF1R gene have been reported in patients with varying degrees of intrauterine and postnatal growth retardation.
Objective:
The objective of the study was the analysis of the IGF1R gene in a short-statured patient.
Patient:
The male patient, with a height of −5.91 sd score (aged 20.3 yr), had consistently elevated circulating serum concentrations of IGF-I. A diagnosis of antibody-negative insulin-requiring diabetes was made at age 14 yr. His deceased sister was also severely short statured (−3.75 sd score).
Results:
The patient and his sister carried novel, compound heterozygous IGF1R missense mutations, E121K (exon 2) and E234K (exon 3), inherited from the mother and father, respectively. In vitro reconstitution studies demonstrated that neither the E121K nor E234K mutation affected IGF1R prepeptide expression, but levels of the proteolytically cleaved α- and β-subunit were consistently low. As a consequence, each IGF1R variant exhibited significantly reduced IGF-I-induced signal transduction. Correlating to these studies, expression of functional IGF1R and the IGF-I-induced activation of the IGF1R pathway were markedly reduced in the primary dermal fibroblasts established from the patient.
Conclusions:
Only the second compound heterozygous IGF1R mutations to be identified, the p.E121K/E234K variant is the cause of intrauterine growth retardation and the most severe postnatal growth failure described to date in a patient with IGF1R defects. Whether the mutant IGF1R also contributes to the diabetic phenotype, however, remains to be determined.
ACP5 deficiency is known to cause spondyloenchondrodysplasia (SPENCD), which is characterized by various autoimmune and neurological symptoms in addition to short stature.
Two siblings from a ...consanguineous Turkish family, a girl aged 13 years (P1) and a boy aged 8 years (P2), presented to their endocrinologist with progressive growth failure and severe short stature (-5 SDS). They had no comorbid conditions and, on physical examination, there were no signs of an overt skeletal dysplasia with normal appearance of extremities. Other than a low baseline IGF-1, extensive laboratory workup, including growth hormone stimulation and IGF-1 generation tests, was normal. Exome sequencing was performed.
Exome sequencing identified the presence of a homozygous frameshift mutation (p.Ser258Trpfs*39) in ACP5 in both siblings, which was confirmed by Sanger sequencing. This specific mutation has previously been described in patients with SPENCD. Additional workup in the two siblings showed distinct features of skeletal dysplasia on X-rays consistent with SPENCD, but none of the common autoimmune or neurological abnormalities associated with this condition.
Severe short stature can be the only presenting sign of ACP5 deficiency and the latter could therefore be considered as a rare cause in the differential diagnosis of severe, proportionate growth failure.
Context:
Acid labile subunit (ALS) deficiency, caused by IGFALS mutations, is a subtype of primary IGF-I deficiency (PIGFD) and has been associated with insulin resistance (IR) and osteopenia. ...Whether patients respond to recombinant human IGF-I (rhIGF-I) is unknown.
Objective and Design:
This study determined the 14-hour pharmacokinetic response of free and total IGF-I and IGF binding protein 3 (IGFBP-3) to a single sc dose of rhIGF-I (120 μg/kg) in four ALS-deficient patients, compared with severe PIGFD, moderate PIGFD, and controls. Intravenous glucose tolerance tests, fasting blood levels, dual-energy X-ray absorptiometry, peripheral quantitative computed tomography, and metacarpal radiogrammetry were performed in the four patients and 12 heterozygous family members.
Results:
IGF-I and IGFBP-3 increased above baseline (P < .05) for 2.5 hours, returning to baseline 7 hours after rhIGF-I injection. Mean (SD) IGF-I Z-score increased by 2.49 (0.90), whereas IGFBP-3 Z-score increased by 0.57 (0.10) only. IGF-I elimination rates in ALS deficiency were similar, but the IGF-I increment was lower than those for severe PIGFD. Significant gene dosage effects were found for all IGF-I peptides, height, forearm muscle size, and metacarpal width. Bone analysis showed that ALS deficiency creates a phenotype of slender bones with normal size-corrected density. Abnormal glucose handling and IR was found in three of four patients and 6 of 12 carriers.
Conclusions:
These gene dosage effects demonstrate that one functional IGFALS allele is insufficient to maintain normal ALS levels, endocrine IGF-I action, full growth potential, muscle size, and periosteal expansion. Similar gene dosage effects may exist for parameters of IR. Despite similar IGF-I elimination compared with severe PIGFD, ALS-deficient patients cannot mount a similar response. Alternative ways of rhIGF-I administration should be sought.
Context: The central clinical feature of GH insensitivity (GHI) is severe growth failure associated with elevated serum concentrations of GH and abnormally low serum levels of IGF-I. GHI can be the ...result of an abnormality in the GH receptor or aberrancies downstream of the GH receptor.
Objective: We investigated the GH-IGF-I axis in a young female GHI subject who presented with a height of 114 cm (−7.8 sd score) at age 16.4 yr.
Patient: The subject, from a consanguineous pedigree, had circulating levels of GH and GH-binding protein that were normal to elevated, whereas IGF-I (7.2 ng/ml; normal, 242–600), IGF-binding protein-3 (543 ng/ml; normal, 2500–4800), and acid-labile subunit (1.22 μg/ml; normal, 5.6–16) levels were abnormally low and failed to increase during an IGF-I generation test.
Design: Dermal fibroblast cultures were established with the consent of the patient and family. Immunoblot analysis of cell lysates and DNA sequencing of her signal transducer and activator of transcription 5b (STAT5b), a critical intermediate of the GH-IGF-I axis, were performed.
Results: Sequencing of the STAT5b gene revealed a novel homozygous insertion of a single nucleotide in exon 10. The insertion resulted in a frame shift, leading to early protein termination and consequent lack of immunodetectable STAT5b protein.
Conclusion: The identification of a second case of severe growth failure associated with STAT5b mutation implicates a unique and critical role for STAT5b in GH stimulation of IGF-I gene expression and statural growth.
Background: IGF-I, essential for normal human growth in utero and postnatally, mediates its effects through the IGF-I receptor (IGF1R), a widely expressed, cell surface tyrosine kinase receptor. Five ...cases of heterozygous mutations in the IGF1R gene have been identified in patients with varying degrees of intrauterine and postnatal growth retardation.
Objective: The objective of the study was the analysis of the IGF1R gene in a short-statured patient and his affected family members.
Patient: The male patient, with a height of −3.1 sd score (SDS; aged 12 yr), had normal circulating levels of GH binding protein, IGF-I, and IGF binding protein-3. His mother (−4.6 SDS), one of his siblings (−1.94 SDS), and several other maternal family members were also short statured.
Results: The patient, his mother, and the short-statured sibling carry a novel heterozygous 19-nucleotide duplication within exon 18 of the IGF1R gene, which introduces a premature termination codon at codon 1106 of the IGF1R open reading frame on one allele. Analyses of the primary dermal fibroblasts derived from the patient and family members indicated that the IGF1R mRNA expressed from the mutant allele was degraded through the nonsense-mediated mRNA decay pathway, resulting in reduced amount of wild-type IGF1R protein and, subsequently, diminished activation of the IGF1R pathway.
Conclusions: The mutation results in haploinsufficiency of IGF1R protein due to nonsense-mediated mRNA decay and is associated with familial short stature.
A heterozygous mutation in the human IGF1R gene is indentified, which, through nonsense-mediated mRNA decay, results in IGF1R haploinsufficiency and severe short stature.
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