Kinase Activity Is Not Required for G Protein-Coupled Receptor Kinase 4 Restraining mTOR Signaling during Cilia and Kidney Development

SIGNIFICANCE STATEMENT

G protein-coupled receptor kinase 4 (GRK4) regulates renal sodium and water reabsorption. Although GRK4 variants with elevated kinase activity have been associated with salt-sensitive or essential hypertension, this association has been inconsistent among different study populations. In addition, studies elucidating how GRK4 may modulate cellular signaling are sparse. In an analysis of how GRK4 affects the developing kidney, the authors found that GRK4 modulates mammalian target of rapamycin (mTOR) signaling. Loss of GRK4 in embryonic zebrafish causes kidney dysfunction and glomerular cysts. Moreover, GRK4 depletion in zebrafish and cellular mammalian models results in elongated cilia. Rescue experiments suggest that hypertension in carriers of GRK4 variants may not be explained solely by kinase hyperactivity; instead, elevated mTOR signaling may be the underlying cause.

BACKGROUND

G protein-coupled receptor kinase 4 (GRK4) is considered a central regulator of blood pressure through phosphorylation of renal dopaminergic receptors and subsequent modulation of sodium excretion. Several nonsynonymous genetic variants of GRK4 have been only partially linked to hypertension, although these variants demonstrate elevated kinase activity. However, some evidence suggests that function of GRK4 variants may involve more than regulation of dopaminergic receptors alone. Little is known about the effects of GRK4 on cellular signaling, and it is also unclear whether or how altered GRK4 function might affect kidney development.

METHODS

To better understand the effect of GRK4 variants on the functionality of GRK4 and GRK4's actions in cellular signaling during kidney development, we studied zebrafish, human cells, and a murine kidney spheroid model.

RESULTS

Zebrafish depleted of Grk4 develop impaired glomerular filtration, generalized edema, glomerular cysts, pronephric dilatation, and expansion of kidney cilia. In human fibroblasts and in a kidney spheroid model, GRK4 knockdown produced elongated primary cilia. Reconstitution with human wild-type GRK4 partially rescues these phenotypes. We found that kinase activity is dispensable because kinase-dead GRK4 (altered GRK4 that cannot result in phosphorylation of the targeted protein) prevented cyst formation and restored normal ciliogenesis in all tested models. Hypertension-associated genetic variants of GRK4 fail to rescue any of the observed phenotypes, suggesting a receptor-independent mechanism. Instead, we discovered unrestrained mammalian target of rapamycin signaling as an underlying cause.

CONCLUSIONS

These findings identify GRK4 as novel regulator of cilia and of kidney development independent of GRK4's kinase function and provide evidence that the GRK4 variants believed to act as hyperactive kinases are dysfunctional for normal ciliogenesis.

Muscarinic receptors promote pacemaker fate at the expense of secondary conduction system tissue in zebrafish

Deterioration or inborn malformations of the cardiac conduction system (CCS) interfere with proper impulse propagation in the heart and may lead to sudden cardiac death or heart failure. Patients afflicted with arrhythmia depend on antiarrhythmic medication or invasive therapy, such as pacemaker implantation. An ideal way to treat these patients would be CCS tissue restoration. This, however, requires precise knowledge regarding the molecular mechanisms underlying CCS development. Here, we aimed to identify regulators of CCS development. We performed a compound screen in zebrafish embryos and identified tolterodine, a muscarinic receptor antagonist, as a modifier of CCS development. Tolterodine provoked a lower heart rate, pericardiac edema, and arrhythmia. Blockade of muscarinic M3, but not M2, receptors induced transcriptional changes leading to amplification of sinoatrial cells and loss of atrioventricular identity. Transcriptome data from an engineered human heart muscle model provided additional evidence for the contribution of muscarinic M3 receptors during cardiac progenitor specification and differentiation. Taken together, we found that muscarinic M3 receptors control the CCS already before the heart becomes innervated. Our data indicate that muscarinic receptors maintain a delicate balance between the developing sinoatrial node and the atrioventricular canal, which is probably required to prevent the development of arrhythmia.

Resting cells rely on the DNA helicase component MCM2 to build cilia

Minichromosome maintenance (MCM) proteins facilitate replication by licensing origins and unwinding the DNA double strand. Interestingly, the number of MCM hexamers greatly exceeds the number of firing origins suggesting additional roles of MCMs. Here we show a hitherto unanticipated function of MCM2 in cilia formation in human cells and zebrafish that is uncoupled from replication. Zebrafish depleted of MCM2 develop ciliopathy-phenotypes including microcephaly and aberrant heart looping due to malformed cilia. In non-cycling human fibroblasts, loss of MCM2 promotes transcription of a subset of genes, which cause cilia shortening and centriole overduplication. Chromatin immunoprecipitation experiments show that MCM2 binds to transcription start sites of cilia inhibiting genes. We propose that such binding may block RNA polymerase II-mediated transcription. Depletion of a second MCM (MCM7), which functions in complex with MCM2 during its canonical functions, reveals an overlapping cilia-deficiency phenotype likely unconnected to replication, although MCM7 appears to regulate a distinct subset of genes and pathways. Our data suggests that MCM2 and 7 exert a role in ciliogenesis in post-mitotic tissues.

Imbalanced mitochondrial function provokes heterotaxy via aberrant ciliogenesis

About 1% of all newborns are affected by congenital heart disease (CHD). Recent findings identify aberrantly functioning cilia as a possible source for CHD. Faulty cilia also prevent the development of proper left-right asymmetry and cause heterotaxy, the incorrect placement of visceral organs. Intriguingly, signaling cascades such as mTor that influence mitochondrial biogenesis also affect ciliogenesis, and can cause heterotaxy-like phenotypes in zebrafish. Here, we identify levels of mitochondrial function as a determinant for ciliogenesis and a cause for heterotaxy. We detected reduced mitochondrial DNA content in biopsies of heterotaxy patients. Manipulation of mitochondrial function revealed a reciprocal influence on ciliogenesis and affected cilia-dependent processes in zebrafish, human fibroblasts and Tetrahymena thermophila. Exome analysis of heterotaxy patients revealed an increased burden of rare damaging variants in mitochondria-associated genes as compared to 1000 Genome controls. Knockdown of such candidate genes caused cilia elongation and ciliopathy-like phenotypes in zebrafish, which could not be rescued by RNA encoding damaging rare variants identified in heterotaxy patients. Our findings suggest that ciliogenesis is coupled to the abundance and function of mitochondria. Our data further reveal disturbed mitochondrial function as an underlying cause for heterotaxy-linked CHD and provide a mechanism for unexplained phenotypes of mitochondrial disease.

Analysis of cilia dysfunction phenotypes in zebrafish embryos depleted of Origin recognition complex factors

Meier-Gorlin syndrome (MGS) is a rare, congenital primordial microcephalic dwarfism disorder. MGS is caused by genetic variants of components of the origin recognition complex (ORC) consisting of ORC1-6 and the pre-replication complex, which together enable origin firing and hence genome replication. In addition, ORC1 has previously been shown to play a role in ciliogenesis. Here, we extend this work and investigate the function of ORC1 and two other members of the complex on cilia at an organismal level. Knockdown experiments in zebrafish confirmed the impact of ORC1 on cilia. ORC1-deficiency confers defects anticipated to arise from impaired cilia function such as formation of oedema, kidney cysts, curved bodies and left-right asymmetry defects. We found ORC1 furthermore required for cilium formation in zebrafish and demonstrate that ciliopathy phenotypes in ORC1-depleted zebrafish could not be rescued by reconstitution with ORC1 bearing a genetic variant previously identified in MGS patients. Loss-of-function of Orc4 and Orc6, respectively, conferred similar ciliopathy phenotypes and cilium shortening in zebrafish, suggesting that several, if not all, components of the ORC regulate ciliogenesis downstream to or in addition to their canonical function in replication initiation. This study presents the first in vivo evidence of an influence of the MGS genes of the ORC family on cilia, and consolidates the possibility that cilia dysfunction could contribute to the clinical manifestation of ORC-deficient MGS.

Characterization of Danio rerio Nanog and functional comparison to Xenopus Vents

Nanog is a homeodomain transcription factor associated with the acquisition of pluripotency. Genome analyses of lower and higher vertebrates revealed that the existence of Nanog is restricted to gnathostomata but absent from agnatha and invertebrates. To elucidate the function of Nanog in nonmammalia, we identified the Danio rerio ortholog of Nanog and characterized its role in gain and loss of function experiments. We found Nanog to be crucial for survival of early zebrafish embryos, because depletion of Nanog led to gastrulation defects with subsequent lethality. Mouse Nanog overexpression could rescue these defects. Vice versa, zebrafish Nanog was found to promote proliferation and to inhibit differentiation of mouse embryonic stem cells in the absence of leukemia inhibitory factor. These findings indicate functional conservation of Nanog from teleost fishes to mammals. However, Nanog was lost in the genome of the anurans Xenopus laevis and Xenopus tropicalis. Phylogenetic analysis revealed that deletion probably occurred in a common anuran ancestor along with chromosomal translocations. The closest homologs of Nanog in Xenopus are the Vent proteins. We, therefore, investigated whether the Xvent genes might substitute for Nanog function in Xenopus. Although we found some similarities in phenotypes after overexpression and in the regulation of several marker genes, Xvent1/2 and Nanog cannot substitute each other. Depletion of Nanog in zebrafish cannot be rescued by ectopic expression of Xvent, and Xvent depletion in Xenopus cannot be overcome by ectopic expression of zebrafish Nanog.

FoxO genes are dispensable during gastrulation but required for late embryogenesis in Xenopus laevis

Forkhead box (Fox) transcription factors of subclass O are involved in cell survival, proliferation, apoptosis, cell metabolism and prevention of oxidative stress. FoxO genes are highly conserved throughout evolution and their functions were analyzed in several vertebrate and invertebrate organisms. We here report on the identification of FoxO4 and FoxO6 genes in Xenopus laevis and analyze their expression patterns in comparison with the previously described FoxO1 and FoxO3 genes. We demonstrate significant differences in their temporal and spatial expression during embryogenesis and in their relative expression within adult tissues. Overexpression of FoxO1, FoxO4 or FoxO6 results in severe gastrulation defects, while overexpression of FoxO3 reveals this defect only in a constitutively active form containing mutations of Akt-1 target sites. Injections of FoxO antisense morpholino oligonucleotides (MO) did not influence gastrulation, but, later onwards, the embryos showed a delay of development, severe body axis reduction and, finally, a high rate of lethality. Injection of FoxO4MO leads to specific defects in eye formation, neural crest migration and heart development, the latter being accompanied by loss of myocardin expression. Our observations suggest that FoxO genes in X. laevis are dispensable until blastopore closure but are required for tissue differentiation and organogenesis.

Two Hoxc6 transcripts are differentially expressed and regulate primary neurogenesis in Xenopus laevis

Hox genes are key players in defining positional information along the main body axis of vertebrate embryos. In Xenopus laevis, Hoxc6 was the first homeobox gene isolated. It encodes two isoforms. We analyzed in detail their spatial and temporal expression pattern during early development. One major expression domain of both isoforms is the spinal cord portion of the neural tube. Within the spinal cord and its populations of primary neurons, Hox genes have been found to play a crucial role for defining positional information. Here we report that a loss-of-function of either one of the Hoxc6 products does not affect neural induction, the expression of general neural markers is not modified. However, Hoxc6 does widely affect the formation of primary neurons within the developing neural tissue. Manipulations of Hoxc6 expression severly changes the expression of the neuronal markers N-tubulin and Islet-1. Formation of primary neurons and formation of cranial nerves are affected. Hence, Hoxc6 functions are not restricted to the expected role in anterior-posterior pattern formation, but they also regulate N-tubulin, thereby having an effect on the initial formation of primary neurons in Xenopus laevis embryos.

POU-V factors antagonize maternal VegT activity and beta-Catenin signaling in Xenopus embryos

VegT and beta-Catenin are key players in the hierarchy of factors that are required for induction and patterning of mesendoderm in Xenopus embryogenesis. By descending the genetic cascades, cells lose their pluripotent status and are determined to differentiate into distinct tissues. Mammalian Oct-3/4, a POU factor of subclass V (POU-V), is required for the maintenance of pluripotency of embryonic stem cells. However, its molecular function within the early embryo is yet poorly understood. We here show that the two maternal Xenopus POU-V factors, Oct-60 and Oct-25, inhibit transcription of genes activated by VegT and beta-Catenin. Maternal POU-V factors and maternal VegT show an opposite distribution along the animal/vegetal axis. Oct-25, VegT and Tcf3 interact with each other and form repression complexes on promoters of VegT and beta-Catenin target genes. We suggest that POU-V factors antagonize primary inducers to allow germ layer specification in a temporally and spatially coordinated manner.

FoxN3 is required for craniofacial and eye development of Xenopus laevis

A functional knockdown of FoxN3, a member of subclass N of fork head/winged helix transcription factors in Xenopus laevis, leads to an abnormal formation of the jaw cartilage, absence or malformation of distinct cranial nerves, and reduced size of the eye. While the eye phenotype is due to an increased rate of apoptosis, the cellular basis of the jaw phenotype is more complex. The upper and lower jaw cartilages are derivatives of a subset of cranial neural crest cells, which migrate into the first pharyngeal arch. Histological analysis of FoxN3-depleted embryos reveals severe deformation and false positioning of infrarostral, Meckel's, and palatoquadrate cartilages, structural elements derived from the first pharyngeal arch, and of the ceratohyale, which derives from the second pharyngeal arch. The derivatives of the third and fourth pharyngeal arches are less affected. FoxN3 is not required for early neural crest migration. Defects in jaw formation rather arise by failure of differentiation than by positional effects of crest migration. By GST-pulldown analysis, we have identified two different members of histone deacetylase complexes (HDAC), xSin3 and xRPD3, as putative interaction partners of FoxN3, suggesting that FoxN3 regulates craniofacial and eye development by recruiting HDAC.

The FoxP subclass in Xenopus laevis development

We have investigated the sequences and the expression patterns of different members of the Xenopus laevis FoxP gene subfamily during embryogenesis. Low stringency hybridisation of a tadpole cDNA library with an xlFoxP2 fragment led to the isolation of several splice variants of xlFoxP1, xlFoxP2 and xlFoxP4. These variants do not only differ by utilisation of different leader exons, but also by alternative usage of coding exons thereby leading to functional alterations. For xlFoxP1b, we show that insertion of an additional exon disrupts binding to the co-repressor C-terminal binding protein1. Temporal and spatial expression patterns of xlFoxP2 and xlFoxP4 were analysed by RT-PCR and by whole mount in situ hybridisation. xlFoxP2 transcripts are detected from mid-gastrula to late tadpole stages and are found to be localised to pronephros, branchial arches and distinct structures of the hind-, mid- and forebrain, including the ciliary marginal zone of the retina. xlFoxP4 RNA is already present in early cleavage stage embryos and accumulates from midblastula until the end of embryogenesis. Localised expression is found within the anterior neural fold, in the mid- and hindbrain, in the branchial arches as well as in the pancreas.

Temporal and spatial expression patterns of FoxN genes in Xenopus laevis embryos

Using RT-PCR and in situ hybridisation, we have analysed the temporal and spatial expression patterns of Xenopus Fox genes of subclass N. By screening cDNA libraries and by RT-PCR using embryonic RNA and primers derived from EST analyses, we could isolate FoxN2, FoxN4, FoxN5 and different isoforms of FoxN3. FoxN2 and FoxN3 transcripts were found during all developmental stages including early cleavage and tailbud stages. FoxN5 transcripts were only present at early cleavage stages, while FoxN4 expression began after midblastula transition. Spatial expression of FoxN2 was first detected in the early eye field and later, in the branchial arches, the vagal ganglion and in the developing retina. FoxN3 transcripts were found within the animal cap. In post-gastrula embryos, neural crest cells and the early eye field showed strong expression of FoxN3. At late tadpole stages, the branchial arches were stained. FoxN4 was expressed in the early eye field and later in the developing retina cells, the nephrostomes of the pronephric kidney and in the midbrain. A ubiquitous expression of FoxN5 was found in early cleavage stage embryos.

XBP1 forms a regulatory loop with BMP-4 and suppresses mesodermal and neural differentiation in Xenopus embryos

The active form of the Xenopus X-box binding protein 1 (xXBP1) partially synergizes and partially antagonizes with BMP-4 signaling. xXBP1 overexpression inhibits mesoderm differentiation and formation of neural tissues. A functional knockdown promotes differentiation of lateral and dorsal mesoderm but not of ventral mesoderm and of neuroectoderm. We show that the active form of xXBP1 in gastrula and early neurula stage embryos is generated by removal of exon 4 and not by an endoribonuclease activity in the endoplasmic reticulum. The N-terminal region of xXBP1 which contains the basic leucine-zipper also contains a nuclear localization signal and both, the N-terminal as well as the C-terminal regions are required for xXBP1 function. The effects of xXBP1 are in part correlated to a regulatory loop between xXBP1 and BMP-4. xXBP1 and BMP-4 stimulate mutually the transcription of each other, but xXBP1 inhibits the BMP-4 target gene, Xvent-2. Both, in vitro and in vivo assays demonstrate that xXBP1 interacts with BMP-4 and Xvent-2B promoters. GST-pulldown assays reveal that xXBP1 can interact with c-Jun, the transcriptional co-activator p300 and with the BMP-4 responsive Smad1. On the other hand, xXBP1 also binds to the inhibitory Smads, Smad6 and Smad7, that can act as transcriptional co-repressors. Based on these data, we conclude that xXBP1 might function as an inhibitor of mesodermal and neural tissue formation by acting either as transcriptional activator or as repressor. This dual activity depends upon binding of co-factors being involved in the formation of distinct transcription complexes.

The POU factor Oct-25 regulates the Xvent-2B gene and counteracts terminal differentiation in Xenopus embryos

The Xvent-2B promoter is regulated by a BMP-2/4-induced transcription complex comprising Smad signal transducers and specific transcription factors. Using a yeast one-hybrid screen we have found that Oct-25, a Xenopus POU domain protein related to mammalian Oct-3/4, binds as an additional factor to the Xvent-2B promoter. This interaction was further confirmed by both in vitro and in vivo analyses. The Oct-25 gene is mainly transcribed during blastula and gastrula stages in the newly forming ectodermal and mesodermal germ layers. Luciferase reporter gene assay demonstrated that Oct-25 stimulates transcription of the Xvent-2B gene. This stimulation depends on the Oct-25 binding site and the bone morphogenetic protein-responsive element. Furthermore, Oct-25 interacts in vitro with components of the Xvent-2B transcription complex, like Smad1/4 and Xvent-2. Overexpression of Oct-25 results in anterior/posterior truncations and lack of differentiation for neuroectoderm- and mesoderm-derived tissues including blood cells. This effect is consistent with an evolutionarily conserved role of class V POU factors in the maintenance of an undifferentiated cell state. In Xenopus, the molecular mechanism underlying this process might be coupled to the expression of Xvent proteins.

The influence of hydroxyapatite granules on the healing of a segmental defect filled with autologous bone marrow

Hydroxyapatite(HA) ceramics are frequently used as a bone graft substitutes for the filling of bony defects. The addition of autologous bone marrow to HA ceramics does improve defect healing. There is conflicting evidence in the literature whether autologous bone marrow transplantation alone is as effective as the combination of HA ceramics and bone marrow combined. It was the purpose of this study to identify the role of additional HA ceramic granules on the healing of a sheep tibia segmental defect filled with autologous bone marrow. After permission of the local animal rights committee was obtained, a 3 cm segmental defect in the midshaft of 31 adult sheep was stabilized with an unreamed tibia nail. The animals were divided into 4 groups according to the mode of defect filling: HA plus autologous bone marrow (HA + MAR) (n = 8), autologous bone marrow (MAR) (n = 9), empty defect (DEF) (n = 6), cancellous bone graft (CAN) (n = 8). After three months follow up animals were sacrificed and analysed for the key parameters of union and maximum torque at failure. One nonunion was present in each of the HA + MAR, MAR, and CAN groups. Four of the six animals in the DEF group developed a nonunion. Maximum torque at failure was reported as percentage of the intact contralateral tibia: HA + MAR 39% +/- 24%, MAR 26% +/- 17%, DEF 22% +/- 13%, CAN 41% +/- 20%. The difference between the groups was statistically significant, but appeared to be relevant. We conclude from our data, that HA ceramics do improve healing of a segmental defect in the sheep tibia filled with autologous bone marrow. The results of this combination are comparable to cancellous autograft.

Recurrent rotational deformity of the femur after static locking of intramedullary nails: case reports

Rotational deformity following intramedullary nailing may cause symptoms and require surgical correction by osteotomy. Reamed, locked intramedullary nailing may be performed, but concern about cortical blood supply and potential pulmonary dysfunction from reaming have led many surgeons to limit this and use smaller diameter nails. Slotted nails are commonly used but are less stiff in torsion than the newer unslotted nails, particularly at the lower diameters. We report two cases of recurrent femoral rotational deformity after using statically interlocked slotted intramedullary nails to correct existing femoral rotational deformities. These patients show that small diameter statically interlocked femoral nails with diminished bone-nail contact must be stiff enough in rotation to avoid potential recurrence.

Bifurcate tracheal stent with foam cuff for tracheo-esophageal fistula: utilization of reconstruction modes of spiral computed tomography

Malignant tracheo-esophageal fistulae can be palliated with bifurcate tracheal stents. However, stents must be manufactured according to the individual anatomy. In these instances a foam cuff can result in better sealing of the fistulized area. We present a successful implantation of a bifurcate tracheal stent with foam cuff. To facilitate preoperative planning reconstruction possibilities offered by spiral computed tomography were used.

Pathologic aspects of gastrinomas in patients with Zollinger-Ellison syndrome with and without multiple endocrine neoplasia type I

During the three decades since the recognition of the Zollinger-Ellison syndrome (ZES), major progress has been made in the diagnosis and treatment of this disease. However, the many failed operations in patients with ZES, the existence of primary lymph node gastrinomas, and the surgical approach of patients with ZES and multiple endocrine neoplasia type I (MEN-I) have remained controversial issues. In this review, our experience with the pathology of immunocytochemically identified gastrinomas in 44 patients with ZES is presented and related to the relevant literature. (1) Gastrinomas occur frequently in the duodenum (> 40%) and are commonly small (< 1 cm). They can therefore easily be missed at surgical exploration; lymph node metastases from such occult gastrinomas may be mistaken for primary tumors. (2) Most pancreatic gastrinomas reside in the head of the gland and have a diameter of 1 to 3 cm. (3) Gastrinomas associated with MEN-I are predominantly of duodenal origin and frequently multicentric; sporadic gastrinomas are single and more often pancreatic. Because MEN-I associated pancreatic tumors seldom contain gastrin, ZES in MEN-I patients is almost never cured by resection of the pancreatic tumors. (4) The metastatic potential of most small duodenal gastrinomas seems to be restricted to the regional lymph nodes.

Nuclear DNA content in 27 pancreatic endocrine tumours: correlation with malignancy, survival and expression of glycoprotein hormone alpha chain

Paraffin-embedded tissue from resection specimens of 14 functioning and 13 nonfunctioning pancreatic endocrine tumours (PET) was analysed for nuclear DNA content by image cytometry. Data on follow-up (mean 5.5 years) were available in all patients. DNA histograms with a diploid pattern were found in 13 (48%) tumours, while an aneuploid pattern was seen in the remaining 14 tumours (52%). Six (40%) of the diploid tumours and 9 (60%) of the aneuploid tumours were malignant. Survival was shorter in patients with malignant and aneuploid PET (mean 3.5 years, range 0.5-7) than in those with malignant and diploid PET (mean 5.7 years, range 3-8). Human chorionic gonadotropin-alpha was expressed in 3 of 12 benign PET, with 1 being aneuploid, and 6 of 15 malignant PET, with 4 being aneuploid. We conclude from these results that the ploidy pattern of PET allows no discrimination between benign and malignant tumours but may provide prognostic information on the aggressiveness of malignant PET.

Surgical pathology of gastrinoma. Site, size, multicentricity, association with multiple endocrine neoplasia type 1, and malignancy

Specimens from the pancreas and duodenum of 26 patients with sporadic Zollinger-Ellison syndrome (ZES) and 18 patients with multiple endocrine neoplasia type 1 (MEN-1) and hypergastrinemia (17 with ZES) were screened immunocytochemically for gastrinomas. Location, size, multicentricity, and malignancy of the gastrinomas were evaluated. The MEN-1 patients had gastrinomas in the duodenum (nine of 18), pancreas (one of 18), and periduodenal lymph nodes (two of 18). No gastrinoma was identified in six patients. Most duodenal gastrinomas were multiple (five of nine) and smaller than 0.6 cm (six of nine). Lymph node metastases were present in eight of 12 patients. All 26 patients with sporadic ZES had a solitary gastrinoma; 14 were found in the pancreas and had a diameter greater than 2 cm. Ten patients had a duodenal gastrinoma, two with a diameter less than 0.6 cm. In two patients, only periduodenal "lymph node gastrinomas" were detected. Eighteen of the sporadic gastrinomas were malignant. These results suggest that duodenal location and multicentricity of gastrinomas are associated with the MEN-1 syndrome, and solitary gastrinomas, either in the pancreas or the duodenum, are predominantly seen in sporadic ZES.

Surgical pathology of gastrinoma. Site, size, multicentricity, association with multiple endocrine neoplasia type 1, and malignancy

Specimens from the pancreas and duodenum of 26 patients with sporadic Zollinger-Ellison syndrome (ZES) and 18 patients with multiple endocrine neoplasia type 1 (MEN-1) and hypergastrinemia (17 with ZES) were screened immunocytochemically for gastrinomas. Location, size, multicentricity, and malignancy of the gastrinomas were evaluated. The MEN-1 patients had gastrinomas in the duodenum (nine of 18), pancreas (one of 18), and periduodenal lymph nodes (two of 18). No gastrinoma was identified in six patients. Most duodenal gastrinomas were multiple (five of nine) and smaller than 0.6 cm (six of nine). Lymph node metastases were present in eight of 12 patients. All 26 patients with sporadic ZES had a solitary gastrinoma; 14 were found in the pancreas and had a diameter greater than 2 cm. Ten patients had a duodenal gastrinoma, two with a diameter less than 0.6 cm. In two patients, only periduodenal "lymph node gastrinomas" were detected. Eighteen of the sporadic gastrinomas were malignant. These results suggest that duodenal location and multicentricity of gastrinomas are associated with the MEN-1 syndrome, and solitary gastrinomas, either in the pancreas or the duodenum, are predominantly seen in sporadic ZES.

[The pathology of insulinoma and gastrinoma. The location, size, multicentricity, association with multiple endocrine type-I neoplasms and malignancy]

The pathology of insulinoma and gastrinoma was studied in 81 patients (31 men, 50 women, mean age 48.4 years) suffering from persistent hyperinsulinaemic hypoglycaemia, and in 44 patients (28 men, 16 women, mean age 48.5 years) with Zollinger-Ellison syndrome. Insulinomas were seen in the pancreas of all patients with persistent hyperinsulinaemic hypoglycaemia. In 70 of the 81 patients the insulinoma was solitary, whereas six patients had multiple insulinomas. In five patients with multiple endocrine neoplasia type I, multiple endocrine tumours of the pancreas were visible, only one of them in each case being an insulinoma. 75% of all insulinomas were less than 2 cm in size and 15% were malignant. 18 of the 44 Zollinger-Ellison syndrome patients also had multiple endocrine neoplasia type I. Nine of these patients presented with duodenal gastrinomas which were often multiple and smaller than 0.5 cm. The gastrinoma was located in the pancreas of one of the patients with multiple endocrine neoplasia, in two patients in lymph nodes, and no gastrinoma was identified in the specimens from six patients. 33% of the duodenal gastrinomas had metastasised. Solitary gastrinomas were found in all 26 patients with sporadic Zollinger-Ellison syndrome, 14 being located in the pancreas (diameter over 2 cm in eight cases) and ten in the duodenum (diameter less than 1 cm in seven cases). 16 of these gastrinomas were malignant.