We recently described X-linked acrogigantism (X-LAG) in sporadic cases of infantile gigantism and a few familial cases of pituitary gigantism in the context of the disorder known as familial isolated pituitary adenomas. X-LAG cases with early onset gigantism (in infants or toddlers) shared copy number gains (CNG) of the distal long arm of chromosome X (Xq26.3). In all patients described to date with Xq26.3 CNG and acro-gigantism, the only coding gene sequence shared by all chromosomal defects was that of GPR101. GPR101 is a class A, rhodopsin-like orphan guanine nucleotide-binding protein (G protein)-coupled receptor (GPCR) with no known endogenous ligand. We review what is known about GPR101, specifically its expression profile in human and animal models, the evidence supporting causation of X-LAG and possibly other roles, including its function in growth, puberty and appetite regulation, as well as efforts to identify putative ligands.
Giampaolo Trivellin, Fabio R Faucz, Adrian F Daly, Albert Beckers and Constantine A Stratakis
Graeme B Bolger, Mariana F Bizzi, Sergio V Pinheiro, Giampaolo Trivellin, Lisa Smoot, Mary-Ann Accavitti, Márta Korbonits and Antonio Ribeiro-Oliveira Jr
PDE4 cyclic nucleotide phosphodiesterases regulate cAMP abundance in cells and therefore regulate numerous processes, including cell growth and differentiation. The rat PDE4A5 isoform (human homolog PDE4A4) interacts with the AIP protein (also called XAP2 or ARA-9). Germline mutations in AIP occur in approximately 20% of patients with Familial Isolated Pituitary Adenoma (FIPA) and 20% of childhood-onset simplex somatotroph adenomas. We therefore examined the protein expression of PDE4A4 and the closely related isoform PDE4A8 in normal human pituitary tissue and in pituitary adenomas. PDE4A4 had low expression in normal pituitary but was significantly overexpressed in somatotroph, lactotroph, corticotroph and clinically nonfunctioning gonadotroph adenomas (P<0.0001 for all subtypes). Likewise, PDE4A8 was expressed in normal pituitary and was also significantly overexpressed in the adenoma subtypes (P<0.0001 for all). Among the different adenoma subtypes, corticotroph and lactotroph adenomas were the highest and lowest expressed for PDE4A4, respectively, whereas the opposite was observed for PDE4A8. Naturally occurring oncogenic variants in AIP were shown by a two-hybrid assay to disrupt the ability of AIP to interact with PDE4A5. A reverse two-hybrid screen identified numerous additional variants in the tetratricopeptide repeat (TPR) region of AIP that also disrupted its ability to interact with PDE4A5. The expression of PDE4A4 and PDE4A8 in normal pituitary, their increased expression in adenomatous pituitary cells where AIP is meant to participate, and the disruption of the PDE4A4–AIP interaction by AIP mutants may play a role in pituitary tumorigenesis.
Vladimir Vasilev, Adrian F Daly, Giampaolo Trivellin, Constantine A Stratakis, Sabina Zacharieva and Albert Beckers
Familial isolated pituitary adenoma (FIPA) is one of the most frequent conditions associated with an inherited presentation of pituitary tumors. FIPA can present with pituitary adenomas of any secretory/non-secretory type. Mutations in the gene for the aryl-hydrocarbon receptor interacting protein (AIP) have been identified in approximately 20% of FIPA families and are the most frequent cause (29%) of pituitary gigantism. Pituitary tumors in FIPA are larger, occur at a younger age and display more aggressive characteristics and evolution than sporadic adenomas. This aggressiveness is especially marked in FIPA kindreds with AIP mutations. Special attention should be paid to young patients with pituitary gigantism and/or macroadenomas, as AIP mutations are prevalent in these groups. Duplications on chromosome Xq26.3 involving the gene GPR101 lead to X-linked acrogigantism (X-LAG), a syndrome of pituitary gigantism beginning in early childhood; three kindreds with X-LAG have presented in the setting of FIPA. Management of pituitary adenomas in the setting of FIPA, AIP mutations and GPR101 duplications is often more complex than in sporadic disease due to early onset disease, aggressive tumor growth and resistance to medical therapy.
Paraskevi Xekouki, Spyridon A Mastroyiannis, Dimitrios Avgeropoulos, Maria de la Luz Sierra, Giampaolo Trivellin, Evgenia A Gourgari, Charalampos Lyssikatos, Martha Quezado, Nicholas Patronas, Christina Kanaka-Gantenbein, George P Chrousos and Constantine A Stratakis
Adrian F Daly, Philippe A Lysy, Céline Desfilles, Liliya Rostomyan, Amira Mohamed, Jean-Hubert Caberg, Veronique Raverot, Emilie Castermans, Etienne Marbaix, Dominique Maiter, Chloe Brunelle, Giampaolo Trivellin, Constantine A Stratakis, Vincent Bours, Christian Raftopoulos, Veronique Beauloye, Anne Barlier and Albert Beckers
X-linked acrogigantism (X-LAG) syndrome is a newly described form of inheritable pituitary gigantism that begins in early childhood and is usually associated with markedly elevated GH and prolactin secretion by mixed pituitary adenomas/hyperplasia. Microduplications on chromosome Xq26.3 including the GPR101 gene cause X-LAG syndrome. In individual cases random GHRH levels have been elevated. We performed a series of hormonal profiles in a young female sporadic X-LAG syndrome patient and subsequently undertook in vitro studies of primary pituitary tumor culture following neurosurgical resection. The patient demonstrated consistently elevated circulating GHRH levels throughout preoperative testing, which was accompanied by marked GH and prolactin hypersecretion; GH demonstrated a paradoxical increase following TRH administration. In vitro, the pituitary cells showed baseline GH and prolactin release that was further stimulated by GHRH administration. Co-incubation with GHRH and the GHRH receptor antagonist, acetyl-(d-Arg2)-GHRH (1-29) amide, blocked the GHRH-induced GH stimulation; the GHRH receptor antagonist alone significantly reduced GH release. Pasireotide, but not octreotide, inhibited GH secretion. A ghrelin receptor agonist and an inverse agonist led to modest, statistically significant increases and decreases in GH secretion, respectively. GHRH hypersecretion can accompany the pituitary abnormalities seen in X-LAG syndrome. These data suggest that the pathology of X-LAG syndrome may include hypothalamic dysregulation of GHRH secretion, which is in keeping with localization of GPR101 in the hypothalamus. Therapeutic blockade of GHRH secretion could represent a way to target the marked hormonal hypersecretion and overgrowth that characterizes X-LAG syndrome.
Giampaolo Trivellin, Ricardo R Correa, Maria Batsis, Fabio R Faucz, Prashant Chittiboina, Ivana Bjelobaba, Darwin O Larco, Martha Quezado, Adrian F Daly, Stanko S Stojilkovic, T John Wu, Albert Beckers, Maya B Lodish and Constantine A Stratakis
Cushing’s disease (CD) in children is caused by adrenocorticotropic hormone (ACTH)-secreting pituitary adenomas. Germline or somatic mutations in genes such as MEN1, CDKIs, AIP, and USP8 have been identified in pediatric CD, but the genetic defects in a significant percentage of cases are still unknown. In this study, we investigated the orphan G-protein-coupled receptor GPR101, a gene known to be involved in somatotropinomas, for its possible involvement in corticotropinomas. We performed GPR101 sequencing, expression analyses by RT-qPCR and immunostaining, and functional studies (cell proliferation, pituitary hormone secretion, and cAMP measurement) in a series of patients with sporadic CD secondary to ACTH-secreting adenomas in whom we extracted DNA from peripheral blood and pituitary tumor samples (n=36). No increased GPR101 expression was observed in tumors compared with normal pituitary (NP) tissues, nor did we find a correlation between GPR101 and ACTH expression levels. Sequence analysis revealed a very rare germline heterozygous GPR101 variant (p.G31S) in one patient with CD. Overexpression of the p.G31S variant did not lead to increased growth and proliferation, although modest effects on cAMP signaling were observed. GPR101 is not overexpressed in ACTH-secreting tumors compared with NPs. In conclusion, rare germline GPR101 variant was found in one patient with CD, but in vitro studies did not support a consistent pathogenic effect. GPR101 is unlikely to be involved in the pathogenesis of CD.
Fabio R Faucz, Anelia D Horvath, Monalisa F Azevedo, Isaac Levy, Beata Bak, Ying Wang, Paraskevi Xekouki, Eva Szarek, Evgenia Gourgari, Allison D Manning, Rodrigo Bertollo de Alexandre, Emmanouil Saloustros, Giampaolo Trivellin, Maya Lodish, Paul Hofman, Yvonne C Anderson, Ian Holdaway, Edward Oldfield, Prashant Chittiboina, Maria Nesterova, Nienke R Biermasz, Jan M Wit, Daniel J Bernard and Constantine A Stratakis
IGSF1 is a membrane glycoprotein highly expressed in the anterior pituitary. Pathogenic mutations in the IGSF1 gene (on Xq26.2) are associated with X-linked central hypothyroidism and testicular enlargement in males. In this study, we tested the hypothesis that IGSF1 is involved in the development of pituitary tumors, especially those that produce growth hormone (GH). IGSF1 was sequenced in 21 patients with gigantism or acromegaly and 92 healthy individuals. Expression studies with a candidate pathogenic IGSF1 variant were carried out in transfected cells and immunohistochemistry for IGSF1 was performed in the sections of GH-producing adenomas, familial somatomammotroph hyperplasia, and in normal pituitary. We identified the sequence variant p.N604T, which in silico analysis suggested could affect IGSF1 function, in two male patients and one female with somatomammotroph hyperplasia from the same family. Of 60 female controls, two carried the same variant and seven were heterozygous for other variants. Immunohistochemistry showed increased IGSF1 staining in the GH-producing tumor from the patient with the IGSF1 p.N604T variant compared with a GH-producing adenoma from a patient negative for any IGSF1 variants and with normal control pituitary tissue. The IGSF1 gene appears polymorphic in the general population. A potentially pathogenic variant identified in the germline of three patients with gigantism from the same family (segregating with the disease) was also detected in two healthy female controls. Variations in IGSF1 expression in pituitary tissue in patients with or without IGSF1 germline mutations point to the need for further studies of IGSF1 action in pituitary adenoma formation.
Laura C Hernández-Ramírez, Ryhem Gam, Nuria Valdés, Maya B Lodish, Nathan Pankratz, Aurelio Balsalobre, Yves Gauthier, Fabio R Faucz, Giampaolo Trivellin, Prashant Chittiboina, John Lane, Denise M Kay, Aggeliki Dimopoulos, Stephan Gaillard, Mario Neou, Jérôme Bertherat, Guillaume Assié, Chiara Villa, James L Mills, Jacques Drouin and Constantine A Stratakis
The CABLES1 cell cycle regulator participates in the adrenal–pituitary negative feedback, and its expression is reduced in corticotropinomas, pituitary tumors with a largely unexplained genetic basis. We investigated the presence of CABLES1 mutations/copy number variations (CNVs) and their associated clinical, histopathological and molecular features in patients with Cushing’s disease (CD). Samples from 146 pediatric (118 germline DNA only/28 germline and tumor DNA) and 35 adult (tumor DNA) CD patients were screened for CABLES1 mutations. CNVs were assessed in 116 pediatric CD patients (87 germline DNA only/29 germline and tumor DNA). Four potentially pathogenic missense variants in CABLES1 were identified, two in young adults (c.532G > A, p.E178K and c.718C > T, p.L240F) and two in children (c.935G > A, p.G312D and c.1388A > G, and p.D463G) with CD; no CNVs were found. The four variants affected residues within or close to the predicted cyclin-dependent kinase-3 (CDK3)-binding region of the CABLES1 protein and impaired its ability to block cell growth in a mouse corticotropinoma cell line (AtT20/D16v-F2). The four patients had macroadenomas. We provide evidence for a role of CABLES1 as a novel pituitary tumor-predisposing gene. Its function might link two of the main molecular mechanisms altered in corticotropinomas: the cyclin-dependent kinase/cyclin group of cell cycle regulators and the epidermal growth factor receptor signaling pathway. Further studies are needed to assess the prevalence of CABLES1 mutations among patients with other types of pituitary adenomas and to elucidate the pituitary-specific functions of this gene.
Adrian F Daly, Bo Yuan, Frederic Fina, Jean-Hubert Caberg, Giampaolo Trivellin, Liliya Rostomyan, Wouter W de Herder, Luciana A Naves, Daniel Metzger, Thomas Cuny, Wolfgang Rabl, Nalini Shah, Marie-Lise Jaffrain-Rea, Maria Chiara Zatelli, Fabio R Faucz, Emilie Castermans, Isabelle Nanni-Metellus, Maya Lodish, Ammar Muhammad, Leonor Palmeira, Iulia Potorac, Giovanna Mantovani, Sebastian J Neggers, Marc Klein, Anne Barlier, Pengfei Liu, L’Houcine Ouafik, Vincent Bours, James R Lupski, Constantine A Stratakis and Albert Beckers
Somatic mosaicism has been implicated as a causative mechanism in a number of genetic and genomic disorders. X-linked acrogigantism (XLAG) syndrome is a recently characterized genomic form of pediatric gigantism due to aggressive pituitary tumors that is caused by submicroscopic chromosome Xq26.3 duplications that include GPR101. We studied XLAG syndrome patients (n = 18) to determine if somatic mosaicism contributed to the genomic pathophysiology. Eighteen subjects with XLAG syndrome caused by Xq26.3 duplications were identified using high-definition array comparative genomic hybridization (HD-aCGH). We noted that males with XLAG had a decreased log2 ratio (LR) compared with expected values, suggesting potential mosaicism, whereas females showed no such decrease. Compared with familial male XLAG cases, sporadic males had more marked evidence for mosaicism, with levels of Xq26.3 duplication between 16.1 and 53.8%. These characteristics were replicated using a novel, personalized breakpoint junction-specific quantification droplet digital polymerase chain reaction (ddPCR) technique. Using a separate ddPCR technique, we studied the feasibility of identifying XLAG syndrome cases in a distinct patient population of 64 unrelated subjects with acromegaly/gigantism, and identified one female gigantism patient who had had increased copy number variation (CNV) threshold for GPR101 that was subsequently diagnosed as having XLAG syndrome on HD-aCGH. Employing a combination of HD-aCGH and novel ddPCR approaches, we have demonstrated, for the first time, that XLAG syndrome can be caused by variable degrees of somatic mosaicism for duplications at chromosome Xq26.3. Somatic mosaicism was shown to occur in sporadic males but not in females with XLAG syndrome, although the clinical characteristics of the disease were similarly severe in both sexes.
Liliya Rostomyan, Adrian F Daly, Patrick Petrossians, Emil Nachev, Anurag R Lila, Anne-Lise Lecoq, Beatriz Lecumberri, Giampaolo Trivellin, Roberto Salvatori, Andreas G Moraitis, Ian Holdaway, Dianne J Kranenburg - van Klaveren, Maria Chiara Zatelli, Nuria Palacios, Cecile Nozieres, Margaret Zacharin, Tapani Ebeling, Marja Ojaniemi, Liudmila Rozhinskaya, Elisa Verrua, Marie-Lise Jaffrain-Rea, Silvia Filipponi, Daria Gusakova, Vyacheslav Pronin, Jerome Bertherat, Zhanna Belaya, Irena Ilovayskaya, Mona Sahnoun-Fathallah, Caroline Sievers, Gunter K Stalla, Emilie Castermans, Jean-Hubert Caberg, Ekaterina Sorkina, Renata Simona Auriemma, Sachin Mittal, Maria Kareva, Philippe A Lysy, Philippe Emy, Ernesto De Menis, Catherine S Choong, Giovanna Mantovani, Vincent Bours, Wouter De Herder, Thierry Brue, Anne Barlier, Sebastian J C M M Neggers, Sabina Zacharieva, Philippe Chanson, Nalini Samir Shah, Constantine A Stratakis, Luciana A Naves and Albert Beckers
Despite being a classical growth disorder, pituitary gigantism has not been studied previously in a standardized way. We performed a retrospective, multicenter, international study to characterize a large series of pituitary gigantism patients. We included 208 patients (163 males; 78.4%) with growth hormone excess and a current/previous abnormal growth velocity for age or final height >2 s.d. above country normal means. The median onset of rapid growth was 13 years and occurred significantly earlier in females than in males; pituitary adenomas were diagnosed earlier in females than males (15.8 vs 21.5 years respectively). Adenomas were ≥10 mm (i.e., macroadenomas) in 84%, of which extrasellar extension occurred in 77% and invasion in 54%. GH/IGF1 control was achieved in 39% during long-term follow-up. Final height was greater in younger onset patients, with larger tumors and higher GH levels. Later disease control was associated with a greater difference from mid-parental height (r=0.23, P=0.02). AIP mutations occurred in 29%; microduplication at Xq26.3 – X-linked acrogigantism (X-LAG) – occurred in two familial isolated pituitary adenoma kindreds and in ten sporadic patients. Tumor size was not different in X-LAG, AIP mutated and genetically negative patient groups. AIP-mutated and X-LAG patients were significantly younger at onset and diagnosis, but disease control was worse in genetically negative cases. Pituitary gigantism patients are characterized by male predominance and large tumors that are difficult to control. Treatment delay increases final height and symptom burden. AIP mutations and X-LAG explain many cases, but no genetic etiology is seen in >50% of cases.