Prenatal overgrowth and mosaic trisomy 15q25-qter including the IGF1 receptor gene

Components of IGF-axis in growth disorders: a systematic review and patent landscape report

PURPOSE

In this review, epi/genetic mutations of IGF-axis components associated with growth disorders have been summarized alongwith assessment of relevant diagnostic and therapeutic technology through patent literature.

METHODOLOGY

PROSPERO protocol registration CRD42021279468. For scientific literature search Literature databases (PubMed, EMBASE, ScienceDirect, and Google Scholar) were queried using the appropriate syntax. Various filters were applied based on inclusion and exclusion criteria. Search results were further refined by two authors for finalizing studies to be included in this synthesis. For patent documents search Patent databases (Patentscope and Espacenet) were queried using keywords: IGF or IGFBP. Filters were applied according to International Patent Classification (IPC) and Cooperative Patent Classification (CPC). Search results were reviewed by two authors for inclusion in the patent landscape report.

RESULTS

For scientific literature analysis, out of 545 search results, 196 were selected for review based on the inclusion criteria. For Patent literature search, out of 485 results, 37 were selected for this synthesis.

CONCLUSION

Dysregulation of IGF-axis components leads to various abnormalities and their key role in growth and development suggests epi/mutations or structural defects among IGF-axis genes can be associated with growth disorders and may explain some of the idiopathic short stature cases. Trend of patent filings indicate advent of recombinant technology for therapeutics.

Clinical, cytogenetic and molecular analyses of a rare case with ring chromosome 15 and review of the literature

OBJECTIVE

Ring chromosome 15 [r (15)], accompanied by a series of clinical symptoms, is a rare genetic disease. The genotype and phenotypic diversity of patients with r (15) still needed further enrichment. In this study we present a rare case of mosaic ring chromosome 15 with facial anomalies and extremities slenderness.

CASE REPORT

This case involves a 30-year-old woman, unpregnancy within 6 years. Clinical examination of the patient only revealed facial anomalies and extremities slenderness. The result of routine G-band karyotyping was 46,XX,r(15)(p12q26.3)[53]/46,XX,r(15;15)(p11.2q26.3;p11.2q11.2)[28]/45,XX, -15[10]/46,XX,r(15;15)(p11q26.3;p11q26.3)[4]. SNP array was employed to investigate the genome copy number variations (CNVs). The result revealed that there was a micro-duplication of 2.0 Mb at 15q26.3(arr[ph19]15q26.3 (100,400,214- 102,429,112)×3). The duplicated chromosomal section encompassed genes including CHSY1, ALDHIA3, LRRK1, and INS1. We further compared to the cytogenetic characteristics and clinical symptoms of the patient with those already reported by reviewing the literature.

CONCLUSION

This report is especially helpful to supplement the phenotypic diversity of patients with r (15).

Pseudoacromegaly

Individuals with acromegaloid physical appearance or tall stature may be referred to endocrinologists to exclude growth hormone (GH) excess. While some of these subjects could be healthy individuals with normal variants of growth or physical traits, others will have acromegaly or pituitary gigantism, which are, in general, straightforward diagnoses upon assessment of the GH/IGF-1 axis. However, some patients with physical features resembling acromegaly - usually affecting the face and extremities -, or gigantism - accelerated growth/tall stature - will have no abnormalities in the GH axis. This scenario is termed pseudoacromegaly, and its correct diagnosis can be challenging due to the rarity and variability of these conditions, as well as due to significant overlap in their characteristics. In this review we aim to provide a comprehensive overview of pseudoacromegaly conditions, highlighting their similarities and differences with acromegaly and pituitary gigantism, to aid physicians with the diagnosis of patients with pseudoacromegaly.

Chromosome 15 structural abnormalities: effect on IGF1R gene expression and function

Insulin-like growth factor 1 receptor (IGF1R), mapping on the 15q26.3 chromosome, is required for normal embryonic and postnatal growth. The aim of the present study was to evaluate the IGF1R gene expression and function in three unrelated patients with chromosome 15 structural abnormalities. We report two male patients with the smallest 15q26.3 chromosome duplication described so far, and a female patient with ring chromosome 15 syndrome. Patient one, with a 568 kb pure duplication, had overgrowth, developmental delay, mental and psychomotor retardation, obesity, cryptorchidism, borderline low testis volume, severe oligoasthenoteratozoospermia and gynecomastia. We found a 1.8-fold increase in the IGF1R mRNA and a 1.3-fold increase in the IGF1R protein expression (P < 0.05). Patient two, with a 650 kb impure duplication, showed overgrowth, developmental delay, mild mental retardation, precocious puberty, low testicular volume and severe oligoasthenoteratozoospermia. The IGF1R mRNA and protein expression was similar to that of the control. Patient three, with a 46,XX r(15) (p10q26.2) karyotype, displayed intrauterine growth retardation, developmental delay, mental and psychomotor retardation. We found a <0.5-fold decrease in the IGF1R mRNA expression and an undetectable IGF1R activity. After reviewing the previously 96 published cases of chromosome 15q duplication, we found that neurological disorders, congenital cardiac defects, typical facial traits and gonadal abnormalities are the prominent features in patients with chromosome 15q duplication. Interestingly, patients with 15q deletion syndrome display similar features. We speculate that both the increased and decreased IGF1R gene expression may play a role in the etiology of neurological and gonadal disorders.

Two familial microduplications of 15q26.3 causing overgrowth and variable intellectual disability with normal copy number of IGF1R

Terminal duplications of 15q26.3 are associated with an overgrowth phenotype, distinct facial features and intellectual disability, with the smallest reported microduplication to date being 3.16 Mb in size. We report two familial 15q26.3 microduplication cases that are less than half this size, re-defining the minimal critical region for this duplication syndrome. In both families the duplication (albeit a complex copy number gain in one family) is associated with tall stature, early speech delay and variable cognitive problems. Neither familial copy number gains encompass the gene encoding for the insulin-like growth factor 1 receptor (IGF1R), the most-cited candidate for the overgrowth phenotype. In one family, whole genome sequence data and break point mapping excludes disruption of known IGF1R regulatory elements due to potential insertion within these elements. These cases highlight the possibility that the distal region of 15q contains another gene regulating human growth, with LRRK1 being a potential candidate.

A case of de novo duplication of 15q24-q26.3

Distal duplication, or trisomy 15q, is an extremely rare chromosomal disorder characterized by prenatal and postnatal overgrowth, mental retardation, and craniofacial malformations. Additional abnormalities typically include an unusually short neck, malformations of the fingers and toes, scoliosis and skeletal malformations, genital abnormalities, particularly in affected males, and, in some cases, cardiac defects. The range and severity of symptoms and physical findings may vary from case to case, depending upon the length and location of the duplicated portion of chromosome 15q. Most reported cases of duplication of the long arm of chromosome 15 frequently have more than one segmental imbalance resulting from unbalanced translocations involving chromosome 15 and deletions in another chromosome, as well as other structural chromosomal abnormalities. We report a female newborn with a de novo duplication, 15q24-q26.3, showing intrauterine overgrowth, a narrow asymmetric face with down-slanting palpebral fissures, a large, prominent nose, and micrognathia, arachnodactyly, camptodactyly, congenital heart disease, hydronephrosis, and hydroureter. Chromosomal analysis showed a 46,XX,inv(9)(p12q13),dup(15)(q24q26.3). Array comparative genomic hybridization analysis revealed a gain of 42 clones on 15q24-q26.3. This case represents the only reported patient with a de novo 15q24-q26.3 duplication that did not result from an unbalanced translocation and did not have a concomitant monosomic component in Korea.

IGF1R mutations as cause of SGA

Until 2003 monogenetic aberrations that lead to a child that is born too small for gestational age (SGA) were poorly defined. With the first report of mutations within the insulin-like growth factor type 1 receptor (IGF1R) gene in two non-syndromic patients born SGA, who failed to thrive despite normal or even elevated IGF1 serum concentrations the concept of IGF1 resistance has been established. The identification of additional individuals bearing IGF1R mutations along with comparative, genetic, structural and biochemical studies has provided evidence for the pathogenic impact of the IGF1R mutations on human longitudinal growth. However, the variability in the occurrence of additional clinical manifestations, such as developmental delay, might indicate that the pleiotropic functions of the IGF-IGF1R system are partially redundant. It is apparent that we have just begun to unravel the multifaceted IGF1R actions at the interface of growth control, maintenance of metabolic homeostasis and neurodevelopment and neural protection.

A girl with 15q overgrowth syndrome and dup(15)(q24q26.3) that included telomeric sequences

Distal 15q trisomy or tetrasomy is associated with a characteristic phenotype that includes mild to moderate intellectual disability, abnormal behavior, speech impairment, overgrowth, hyperlaxity, long face, prominent nose, puffy cheeks, pointed chin, small ears, and hand anomalies (mainly arachno- and camptodactyly). We present the case of a 13-yr-old girl with the main clinical features of 15q overgrowth syndrome and a 46,XX,dup(15)(q24q26.3)[117]/46,XX[3].ish dup(15)(q24q26.3) (SNPRN+,PML+,subtel++,tel++) de novo karyotype. The findings in this case are consistent with those in the previous distal 15q trisomy cases that presented with overgrowth and mental retardation. Further, the rearranged chromosome had a double set of directly oriented telomeric and subtelomeric sequences.

Distal trisomy of 10q with distal monosomy of 15q due to a paternal translocation

Distal trisomy of 10q is a rare chromosomal abnormality. Distal deletions of the terminal long arm of chromosome 15 have rarely been described. We report on a male infant with low birth weight and microcephaly, a flat face with a spacious forehead, low-set ears, blepharophimosis, microphthalmia, a small nose, and a depressed nasal bridge. Microarray comparative genomic hybridization identified that he had the karyotype 46, XY, der (15) t (10;15) (q25.2;q26.2) pat, with chromosomal breakpoints at 10q25.2 and 15q26.2. This male neonatal case had an unbalanced translocation inherited from his father who was a balanced carrier with the karyotype 46, XY, t (10;15) (q25;q26). The neonate had a partial trisomy of the long arm of chromosome 10 with a partial monosomy of distal 15q. The clinical features were in agreement with previous descriptions and allowed us to propose a growth retardation phenotype for this neonate case.

Tall stature and duplication of the insulin-like growth factor I receptor gene

Trisomy of 15q26-qter is frequently associated with tall stature and mental retardation. Here we describe a patient with such trisomy, without a partial monosomy of another chromosome. The tall stature in this patient is most probably caused by duplication of the IGF1R gene. A duplication of the IGF1R gene is not a frequent finding in patients with tall stature. In 38 patients with features of Sotos syndrome without NSD1 alterations, a duplication was found only once. This patient was already known to have an unbalanced 2;15 translocation. Looking for a duplication of the 15qter region is still worth consideration in patients with tall stature and features of Sotos syndrome without an NSD1 alteration, especially when there is craniosynostosis or marked speech delay.

Intrachromosomal triplication for the distal part of chromosome 15q

We report the case of a boy whose karyotype at birth showed additional material on one chromosome 15. He underwent treatment for unilateral nephroblastoma at 6 years old. At 23 years old, he presented with body asymmetry, facial dysmorphism, arachnodactyly, severe scoliosis, and mental retardation. Molecular cytogenetic analyses of peripheral lymphocytes demonstrated a complex mosaic with three clones. A major cell lineage (68%) showed a chromosome 15 with additional material fused to its telomere long arm that was constituted by an inverted duplicated 15q24.3-qter segment. Therefore, the resulting add(15)(q) harbored an intrachromosomal triplication with the middle segment being inverted in orientation. A minor cell lineage (7%) showed an abnormal chromosome 3 resulting from a telomeric fusion between its short arm and an inverted duplicated 15q24.3-qter segment. The third cell lineage (25%) showed a normal 46,XY constitution. Finally, this resulted in tetrasomy for the distal 15q24.3-qter region in 75% of the patient's lymphocytes. To our knowledge, distal 15q tetrasomy is rare and only eight cases have been reported in the literature, all due to a supernumerary analphoid marker consisting of an inverted duplication. We report here the first observation of distal 15q tetrasomy associated with a 46 chromosomes constitution. We compare the phenotype of our patient to previous cases of distal tetrasomy 15q and discuss the mechanisms underlying this chromosomal rearrangement.