Authorship of Italian medical literature on neuroendocrine neoplasms: any gender gap?

PURPOSE: While males have dominated the physician lines over the last decades the recent female doctors' number increasing might progressively reduce this gender gap. This might be not fully true in the academic/research area. We aimed to analyze the gender distribution of first/senior Italian authors on neuroendocrine neoplasm papers published on peer reviewed journals. METHODS: Publications from January 2019 to September 2023 were reviewed; only papers with first and/or senior Italian authors were included. First/senior author gender, type of article, co-authorship with foreign authors were the variable analyzed. RESULTS: 742 papers with Italian first and/or senior authors were retrieved, 449 (60.5%) multicentric, 285 (38.4%) original articles. A female author was first and senior author in 386/742 (52%) and in 228/742 (31%) papers, respectively. 150 (20.2%) papers included foreign coauthors, being an Italian female researcher first author in 50 papers (33%), senior author in 28 (18.6%). The number of Italian female first/senior authors has been increasing over the years (22 in 2019, 113 in 2022; 16 in 2019, 62 in 2022, respectively). The first/senior female authors were mainly Oncologists/Endocrinologists/Pathologists rather than Gastroenterologists/Nuclear Medicine doctors/Surgeons/Radiologists. CONCLUSION: There has been an increase in the prevalence of female authorship of published research in the neuroendocrine setting over the last 5 years, which partially reflects the current distributions in this field, taking into account that several specialties with different gender distribution are involved. However, senior authorship continues to be primarily men. Efforts should be made to improve proportionate gender representation in both clinical and academic/research setting.

Gastroenteropancreatic grade 3 neuroendocrine tumors: a single entity or a heterogeneous group? A retrospective analysis.

PURPOSE: Grade 3 neuroendocrine tumor (NET G3) is a novel pathologic category within gastro-entero-pancreatic (GEP) neuroendocrine neoplasms (NENs) but its clinical behavior and therapeutic management still remain challenging. Prognostic and predictive factors aiding NET G3 management are needed. PATIENTS AND METHODS: We performed a retrospective analysis from 2015 to 2020 of all patients with > 20% Ki-67, well-differentiated NETs evaluated within our NEN-dedicated multidisciplinary team. We divided the sample according the timing of NET G3 diagnosis, the radiotracers distribution and Ki-67. We analyzed the correlation between these NET G3 features and clinical outcomes. RESULTS: Among 3238 multidisciplinary discussion reports, we selected 55 patients, 48 from GEP and 7 from an occult GEP origin. In 45 patients, NET G3 diagnosis occurred at the beginning of clinical history (upfront-NET G3), whereas in 10, during the NET G1-G2 clinical history (late-NET G3). Patients with ≤ 30% (34/55) vs. > 30% Ki-67 (21/55) had a better overall survival (OS) (p = 0.042); patients with a homogeneous vs. inhomogeneous/negative 68Gallium(68Ga)-DOTA-Peptide Positron Emission Tomography (PET)/computed tomography (CT) showed a trend to a better OS, and a significant better progression-free survival (PFS) (p = 0.033). A better OS was observed for negative/inhomogeneous vs. homogeneous 18-fluorodeoxyglucose (18FDG)-PET/CT (p = 0.027). A trend to a better OS was reported in late- vs. upfront-NET G3, while the latter showed a significantly better response rate (RR) (p = 0.048). CONCLUSION: Our findings suggested that Ki-67 cutoff, functional imaging and the timing to NET G3 diagnosis may help clinicians in more accurate selection of NET G3 management. Prospective studies are needed.

Impact of the SARS-CoV2 pandemic dissemination on the management of neuroendocrine neoplasia in Italy: a report from the Italian Association for Neuroendocrine Tumors (Itanet).

INTRODUCTION: The organization of the healthcare system has significantly changed after the recent COVID-19 outbreak, with a negative impact on the management of oncological patients. The present survey reports data collected by the Italian Association for Neuroendocrine Tumors on the management of patients with neuroendocrine neoplasia (NEN) during the pandemic dissemination. METHODS: A survey with 57 questions was sent to NEN-dedicated Italian centers regarding the management of patients in the period March 9, 2020, to May 9, 2020 RESULTS: The main modification in the centers' activity consisted of decreases in newly diagnosed NEN patients (- 76.8%), decreases in performed surgical procedures (- 58%), delays to starting peptide receptor radionuclide therapy (45.5%), postponed/canceled follow-up examinations (26%), and canceled multidisciplinary teams' activity (20.8%). A low proportion of centers (< 10%) reported having to withdraw systemic anti-tumor medical treatment due to concerns about the pandemic situation, whereas PRRT was withdrawn from no patients. CONCLUSION: Although the COVID-19 outbreak induced the centers to reduce some important activities in the management of NEN patients, the Italian network was able to provide continuity in care without withdrawing anti-tumor treatment for the majority of patients.

Unfavorable carcinoma of unknown primary with a gastrointestinal profile: a retrospective study.

BACKGROUND: Carcinoma of unknown primary (CUP) with a gastrointestinal profile is categorized by the European Society of Medical Oncology (ESMO) guidelines into favorable and unfavorable subsets. Favorable CUPs benefit from site-specific chemotherapy (CT), while the optimal treatment for unfavorable CUPs is still undefined. MATERIALS AND METHODS: We conducted a single-center retrospective study to describe outcomes of patients with CUP with a gastrointestinal profile referred to our center from January 2000 to August 2023. Favorable CUPs were defined as CK7-/CK20+/CDX2+ by immunohistochemistry, according to the ESMO definition; all other cases were considered unfavorable. The main endpoint was the progression-free survival (PFS) of first-line CT for advanced disease in all patients and in the unfavorable group. RESULTS: A total of 56 patients were included, of whom 46 (82%) had unfavorable CUPs. After a median follow-up of 43.9 months, the median overall survival (mOS) was 11.8 months [95% confidence interval (CI) 8.3-15.3 months]. At univariate analysis, the presence of peritoneal metastases and residual tumor after primary surgery were associated with a shorter OS. The median PFS (mPFS) was 6.1 months (95% CI 3.6-8.7 months). In the unfavorable CUP subgroup, the mOS was 12.6 months (95% CI 8.7-16.5 months), the mPFS was 6.1 months (95% CI 3.5-8.9 months) and none of the CT regimens used showed to portend better PFS. The most relevant altered genes included: KRAS (9/29; 31%), BRAF (1/26; 4%), NRAS (1/25; 4%), TP53 (9/23; 39%). CONCLUSIONS: CUPs with a gastrointestinal profile are characterized by poor prognosis and the absence of biomarker for treatment personalization. No CT regimen was superior in terms of PFS in patients with unfavorable CUPs.

Targeting neuroendocrine tumors with octreotide and lanreotide: Key points for clinical practice from NET specialists.

Octreotide and lanreotide are the two somatostatin analogs (SSA) currently available in clinical practice. They have been approved first to control the clinical syndrome (mainly carcinoid syndrome) associated with functioning neuroendocrine tumors (NET) and later for tumor growth control in advanced low/intermediate grade NET. Although evidence regarding their role, especially as antiproliferative therapy, has been increasing over the years some clinical indications remain controversial. Solicited by AIOM (Italian Association of Medical Oncology) a group of clinicians from various specialties, including medical oncology, endocrinology, and gastroenterology, deeply involved in NET for their clinical and research activity, addressed eight open questions, critically reviewing evidence and guidelines and sharing clinical take-home messages. The questions regarded the use of long-acting octreotide and lanreotide in the following settings: functioning and non-functioning NET refractory to label dose, first-line metastatic pulmonary NET, combination with other therapy with an antiproliferative intent, maintenance in NET responding to other therapies, adjuvant treatment, Ki-67-related cut-off, somatostatin receptor imaging, safety, and feasibility. The level of evidence is not absolute for the majority of these clinical contexts, so it is recommended to distinguish routine versus sporadic utilization in very selected cases. Mention of such specific issues by the main European guidelines (ENETS, European Neuroendocrine Tumor Society, and ESMO, European Society for Medical Oncology) was explored and their position reported. However, different clinical decisions on single patients could be made if the case is carefully discussed within a NET-dedicated multidisciplinary team.

Promising targetable biomarkers in pancreatic neuroendocrine tumours.

INTRODUCTION: In the treatment scenario of PanNETs-targeted therapies are desired but limited, as rarity and heterogeneity on PanNETs pose limitations to their development. AREAS COVERED: We performed a literature review searching for promising druggable biomarkers and potential treatments to be implemented in the next future. We focused on treatments which have already reached clinical experimentation, although in early phases. Six targets were identified, namely Hsp90, HIFa, HDACs, CDKs, uPAR, and DDR. Even though biological rational is strong, so far reported efficacy outcomes are quite disappointing. The reason of that should be searched in the patients' heterogeneity, lack of biomarker selection, poor knowledge of interfering mechanisms as well as difficulties in patients accrual. Moreover, different ways to assess treatment efficacy should be considered, other than response rate, in light of the more indolent nature of NETs. EXPERT OPINION: Development of targeted treatments in PanNETs is still an uncovered area, far behind other more frequent cancers. Rarity of NETs led to accrual of unselected populations, possibly jeopardizing the drug efficacy. Better patients' selection, both in terms of topography, grading and biomarkers is crucial and will help understanding which role targeted therapies can really play in these tumors.

Ten years-experience of sunitinib in the treatment of advanced pan-NETs: an update on safety profile.

INTRODUCTION: Sunitinib still represents a milestone in the treatment for progressive, well-differentiated, advanced panNETs. AREAS COVERED: We performed an evidence reappraisal to critically discuss its safety profile. We included nine studies, five clinical trials and four real-world (RW) studies. Within non-real-world (NRW) studies, diarrhea was the most frequent clinical AE. With regard to G3-4 AEs, fatigue and hypertension were the two most frequent, while neutropenia was the most recurrent hematological one. Considering four real-world trials, hand-foot-syndrome (HFS) was the most frequent clinical any-grade AE of any grade and neutropenia was the most common G3-4. Alongside to the AEs rate, the discontinuation rate of sunitinib due to TRAEs was variable among all the nine selected studies, ranging from 10% to 35% in the NRW setting and from 7% to 31% in the RW setting. Conversely, temporary interruption is an accepted strategy to reduce toxicity, even though not specifically tested in pan-NET. EXPERT OPINION: Till now, sunitinib continues to be one of the main therapeutic options for patients with well differentiated advanced panNETs, potentially covering any line of treatment. Therefore, tolerability plays a crucial role to increase adherence to therapy and maximize QoL.

Should temozolomide be used on the basis of O6-methylguanine DNA methyltransferase status in patients with advanced neuroendocrine tumors? A systematic review and meta-analysis.

BACKGROUND: Temozolomide (TEM) is an active treatment in metastatic neuroendocrine tumors (NETs). Patients affected by glioblastoma multiforme or advanced melanoma treated with TEM who have deficiency of O6-methylguanine DNA methyltransferase (MGMT) have a better responses and survival. However, the predictive role of MGMT in patients with NETs treated with TEM is still debated. METHODS: We conducted a systematic review of the literature and meta-analysis, based on PRISMA methodology, searching in the main databases (PubMed, Embase, Scopus, Web of Science, Cochrane Library and clinical trial.gov) and the proceedings of the main international congresses, until April 26, 2021. RESULTS: Twelve out of 616 articles were selected for our analysis, regarding a total of 858 NET patients treated with TEM-based chemotherapy. The status of MGMT had been tested in 513 (60%) patients, using various methods. The pooled overall response rate (ORR) was higher in MGMT-deficient compared with MGMT-proficient NETs, with a risk difference of 0.31 (95% confidence interval, CI: 0.13-0.50; p < 0.001; I2: 73%) and risk ratio of 2.29 (95% CI: 1.34-3.91; p < 0.001; I2: 55%). The pooled progression free survival (PFS) (hazard ratio, HR = 0.56; 95% CI: 0.43-0.74; p < 0.001) and overall survival (OS) (HR = 0.41; 95% CI: 0.20-0.62; p = 0.011) were longer in MGMT-deficient versus MGMT-proficient NETs. CONCLUSIONS: Our meta-analysis suggested that MGMT status may be predictive of TEM efficacy. However, due to the high heterogeneity of the evaluated studies the risk of biases should be considered. On this hypothesis future homogeneous prospective studies are warranted.

CD1d-restricted recognition of synthetic glycolipid antigens by human natural killer T cells.

A conserved subset of mature circulating T cells in humans expresses an invariant Valpha24-JalphaQ T cell receptor (TCR)-alpha chain rearrangement and several natural killer (NK) locus-encoded C-type lectins. These human T cells appear to be precise homologues of the subset of NK1.1(+) TCR-alpha/beta+ T cells, often referred to as NK T cells, which was initially identified in mice. Here we show that human NK T cell clones are strongly and specifically activated by the same synthetic glycolipid antigens as have been shown recently to stimulate murine NK T cells. Responses of human NK T cells to these synthetic glycolipids, consisting of certain alpha-anomeric sugars conjugated to an acylated phytosphingosine base, required presentation by antigen-presenting cells expressing the major histocompatibility complex class I-like CD1d protein. Presentation of synthetic glycolipid antigens to human NK T cells required internalization of the glycolipids by the antigen-presenting cell and normal endosomal targeting of CD1d. Recognition of these compounds by human NK T cells triggered proliferation, cytokine release, and cytotoxic activity. These results demonstrate a striking parallel in the specificity of NK T cells in humans and mice, thus providing further insight into the potential mechanisms of immune recognition by NK T cells and the immunological function of this unique T cell subset.

Self-recognition of CD1 by gamma/delta T cells: implications for innate immunity.

The specificity of immunoglobulins and alpha/beta T cell receptors (TCRs) provides a framework for the molecular basis of antigen recognition. Yet, evolution has preserved a separate lineage of gamma/delta antigen receptors that share characteristics of both immunoglobulins and alpha/beta TCRs but whose antigens remain poorly understood. We now show that T cells of the major tissue gamma/delta T cell subset recognize nonpolymorphic CD1c molecules. These T cells proliferated in response to CD1+ presenter cells, lysed CD1c+ targets, and released T helper type 1 (Th1) cytokines. The CD1c-reactive gamma/delta T cells were cytotoxic and used both perforin- and Fas-mediated cytotoxicity. Moreover, they produced granulysin, an important antimicrobial protein. Recognition of CD1c was TCR mediated, as recognition was transferred by transfection of the gamma/delta TCR. Importantly, all CD1c-reactive gamma/delta T cells express V delta 1 TCRs, the TCR expressed by most tissue gamma/delta T cells. Recognition by this tissue pool of gamma/delta T cells provides the human immune system with the capacity to respond rapidly to nonpolymorphic molecules on professional antigen presenting cells (APCs) in the absence of foreign antigens that may activate or eliminate the APCs. The presence of bactericidal granulysin suggests these cells may directly mediate host defense even before foreign antigen-specific T cells have differentiated.

SARS-CoV-2-related pneumonia can be successfully managed in patients with metastatic neuroendocrine tumors: a critical point of view.

Primary neuroendocrine tumors of the thymus are extremely rare. In patients with advanced disease, tumor growth control, and sometimes also syndrome control are the main goals of systemic therapy. Unfortunately, no standard therapies are available in clinical practice; therefore, clinical studies are strongly recommended. Axitinib (AXI) is a tyrosine kinase inhibitor, currently under investigation in an international phase II/III trial including thymic neuroendocrine tumors. Over the past 5 months, the entire world has been facing a devastating medical emergency brought about by a pandemic due to a novel coronavirus known as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which emerged in Wuhan, China, in late 2019. Since then, health professionals have been expending all their efforts on trying to provide the best available treatments for patients involved. Patients with cancer, especially those with thoracic involvement, are at higher risk of coronavirus disease 19 (COVID-19) and its complications because of their immunosuppressive status caused by the cancer and the anticancer therapies. As it remains unclear how to optimally manage such patients, we wished to report our experience with a patient with a metastatic neuroendocrine tumor of the thymus infected with SARS-CoV-2 in the hope that it may provide some insights and reflections on the management of cancer patients during this challenging time in our history.

Lung carcinoids with high proliferative activity: Further support for the identification of a new tumor category in the classification of lung neuroendocrine neoplasms.

Highly proliferative lung carcinoids (HPLC) have been recently reported but information about this subset remains scarce. OBJECTIVES: Clinical and pathological data of 630 patients with lung carcinoids (LC) referred to Gustave Roussy Institute (GR) and European Institute of Oncology (IEO) were retrospectively reviewed to select HPLC and analyze their frequency, behavior and compare their outcome to conventional LC with Ki-67 ≤ 20 % and mitotic count (MC)≤10/2 mm2. MATERIALS AND METHODS: Selection criteria were: diagnosis of LC confirmed by local pathologist, and available clinical and follow-up data. Patients with Ki-67 > 20 % and/or MC > 10/ 2 mm2 in primary or metastatic specimens were identified as HPLC. RESULTS: 30/514 patients (6%) met the selection criteria of HPLC. Based on primary tumor evaluation, 22/25 (88 %) were classified as atypical carcinoids (AC). Median MC was 4.5/2 mm2 (1-11) 6/2 mm2 (3-15) in primary tumors and metastasis, respectively. Median Ki-67 was respectively 23 % (15-65) and 25 % (8-60). Recurrence rate was 66 % (12/18) in HPLC and 9 % (33/352) in conventional LC. Median RFS was 24 (10-NR) months in HPLC, 288 (141-NR) months in LC with Ki-67 index≤5 % and NR (148-NR) months in LC with Ki-67 6-20% (p < 001). Median OS was 203 (83-NR) months in LC with Ki-67 index≤5%, 101 (79-NR) months in LC with Ki-67 index 6-20 % and 53 (39-NR) months in HPLC (p = 002). Among 20 metastatic patients with HPLC, median PFS under platinum-based chemotherapy, everolimus, alkylating-based chemotherapy, FOLFOX and PRRT was 5.1 (95 % CI 0.7-9.4), 12.1(95 %CI 0.3-24), 6.8 (95 % CI 0-14.9), 10.2 (95 % CI 0.4-19.9) and 14.2 months (95 % CI 0-30) respectively. Best response was stable disease (SD) under platinum-based chemotherapy and partial response (PR) under alkylating-based chemotherapy and FOLFOX. CONCLUSION: This study confirms the existence and rarity of HPLC. Their characteristics and clinical behavior are more similar to LC rather than neuroendocrine carcinomas (NECs), suggesting that this entity could be managed accordingly.

Clinico-pathological features, treatments and survival of malignant insulinomas: a multicenter study.

INTRODUCTION: Management of malignant insulinomas is challenging due to the need to control both hypoglycaemic syndrome and tumor growth. Literature data is limited to small series. AIM OF THE STUDY: To analyze clinico-pathological characteristics, treatments and prognosis of patients with malignant insulinoma. MATERIALS AND METHODS: Multicenter retrospective study on 31 patients (male: 61.3%) diagnosed between 1988 and 2017. RESULTS: The mean age at diagnosis was 48 years. The mean NET diameter was 41 ± 31 mm, and 70.8% of NETs were G2. Metastases were widespread in 38.7%, hepatic in 41.9% and only lymph nodal in 19.4%. In 16.1% of the cases, the hypoglycaemic syndrome occurred after 46 ± 35 months from the diagnosis of originally non-functioning NET, whereas in 83.9% of the cases it led to the diagnosis of NET, of which 42.3% with a mean diagnostic delay of 32.7 ± 39.8 months. Surgical treatment was performed in 67.7% of the cases. The 5-year survival rate was 62%. Overall survival was significantly higher in patients with Ki-67 ≤10% (P = 0.03), insulin level <60 µU/mL (P = 0.015) and in patients who underwent surgery (P = 0.006). Peptide Receptor Radionuclide Therapy (PRRT) was performed in 45.1%, with syndrome control in 93% of patients. CONCLUSIONS: Our study includes the largest series of patients with malignant insulinoma reported to date. The hypoglycaemic syndrome may occur after years in initially non-functioning NETs or be misunderstood with delayed diagnosis of NETs. Surgical treatment and Ki67 ≤10% are prognostic factors associated with better survival. PPRT proved to be effective in the control of hypoglycaemia in majority of cases.

High mobility group 1 protein is not stably associated with the chromosomes of somatic cells.

High mobility group 1 (HMG1) protein is an abundant and conserved component of vertebrate nuclei and has been proposed to play a structural role in chromatin organization, possibly similar to that of histone H1. However, a high abundance of HMG1 had also been reported in the cytoplasm and on the surface of mammalian cells. We conclusively show that HMG1 is a nuclear protein, since several different anti-HMG1 antibodies stain the nucleoplasm of cultured cells, and epitope-tagged HMG1 is localized in the nucleus only. The protein is excluded from nucleoli and is not associated to specific nuclear structures but rather appears to be uniformly distributed. HMG1 can bind in vitro to reconstituted core nucleosomes but is not stably associated to chromatin in live cells. At metaphase, HMG1 is detached from condensed chromosomes, contrary to histone H1. During interphase, HMG1 readily diffuses out of nuclei after permeabilization of the nuclear membranes with detergents, whereas histone H1 remains associated to chromatin. These properties exclude a shared function for HMG1 and H1 in differentiated cells, in spite of their similar biochemical properties. HMG1 may be stably associated only to a very minor population of nucleosomes or may interact transiently with nucleosomes during dynamic processes of chromatin remodeling.

Critical focus on mechanisms of resistance and toxicity of m-TOR inhibitors in pancreatic neuroendocrine tumors.

Pancreatic neuroendocrine tumors (pNETs) are rare neoplasms representing less than 2% of all pancreatic malignancies. The PI3K-AKT-mTOR pathway is often deregulated in pNETs and seems to play a key role in tumorigenesis. Everolimus, an inhibitor of the mTOR pathway, has demonstrated efficacy in the treatment of pNETs. Nevertheless de novo or acquired drug resistance is responsible for disease progression and represents a major obstacle to overcome by clinicians. Blocking the PI3K/AKT/mTOR pathway may cover the supposed main mechanisms of resistance to everolimus. Therefore, BEZ-235, a potent oral dual PI3K/mTOR inhibitor was investigated in clinical trials. Globally more than 250 patients with different types of solid tumors were treated. Two studies were conducted in pNETs with BEZ-235 as single agent. The former was a phase 2 trial conducted in pNETs resistant to everolimus while the latter a randomized trial comparing everolimus and BEZ-235. Unfortunately, both the studies disappointed the expectations and were prematurely halted mainly due to severe toxicity. On this basis we reviewed m-TOR inhibitors in pNETs, focusing on their mechanisms of resistance and toxicity.

Treatments for colorectal liver metastases: A new focus on a familiar concept.

A major challenge for the management of advanced-colorectal-cancer is the multidisciplinary approach required for the treatment of liver metastases. Reducing the burden of liver metastases with liver-directed therapy has an important impact on both survival and health-related quality of life. This paper debates the rationale and current liver-directed approaches for colorectal liver metastases based on the evidence of literature and new clinical trials. Surgery is the gold standard, when feasible, and it's the main treatment goal for patients with potentially-resectable disease as a means of prolonging progression-free survival. Better tumor response rates with modern systemic therapy mean that more unresectable patients are now down-staged for radical resection following conversion therapy but for other patients, additional procedures are needed. In multiple unilobar disease, when the projected remnant liver is <30% of the total liver, portal embolization or selective-internal-radiation-therapy (SIRT) can induce hypertrophy of the healthy liver, leading to resectability. In multiple bilobar disease, in situ destruction of non-resectable lesions by minimally invasive techniques may be associated with liver resection to achieve potential curative intent. Other palliative liver-directed approaches, such as SIRT or intra-hepatic chemotherapy (HAI), which are associated with higher response rates, may also have role in down-staging patients for resection. Until recently, such technologies have not been validated in prospective controlled trials. However in the light of new Phase 3 data for SIRT as well as for HAI combined with modern therapies or radiofrequency ablation in the first- and second-line setting, the clinical value of these treatments needs to be re-appraised.

Inactivation of the zebrafish homologue of Chx10 by antisense oligonucleotides causes eye malformations similar to the ocular retardation phenotype.

We report the cloning of a zebrafish paired-type homeobox gene, Alx, closely related to the murine Chx10 and the gold fish Vsx-I homeodomain proteins. Alx is first expressed at about 12 h post-fertilization (hpf) when optic vesicles appear. Its expression is restricted to the early retinal neuroepithelium, whereas no signal can be detected in the optic placode. Later, Alx expression follows the differentiation of the neural retina. Inhibition experiments with antisense oligonucleotides resulted in specific eye malformations which are reminiscent of the phenotype of ocular retardation (or) mice, caused by a spontaneous Chx10 mutation. The expression of other developmentally relevant genes such as pax(zf-a), pax(zf-b) and krx-20 was not affected in the antisense treated embryos.

High mobility group 1 (HMG1) protein in mouse preimplantation embryos.

High mobility group 1 protein (HMG1) has traditionally been considered a structural component of chromatin, possibly similar in function to histone H1. In fact, at the onset of Xenopus and Drosophila development, HMG1 appears to substitute for histone H1: HMG1 is abundant when histone H1 is absent after the midblastula transition histone H1 largely replaces HMG1. We show that in early mouse embryos the expression patterns of HMG1 and histone H1 are not complementary. Instead, HMG1 content increases after zygotic genome activation at the same time as histone H1. HMG1 does not remain associated to mitotic chromosomes either in embryos or somatic cells. These results argue against a shared structural role for HMG1 and histone H1 in mammalian chromatin.

Evolution of Emx genes and brain development in vertebrates.

Emx1 and Emx2 genes are known to be involved in mammalian forebrain development. In order to investigate the evolution of the Emx gene family in vertebrates, a phylogenetic analysis was carried out on the Emx genes sequenced in man, mice, frogs, coelacanths and zebrafish. The results demonstrated the existence of two clades (Emx1 and Emx2), each grouping one of the two genes of the investigated taxa. The only exception was the zebrafish Emx1-like gene which turned out to be a sister group to both the Emx1 and Emx2 clusters. Such striking sequence divergence observed for the zebrafish Emx1-like gene could indicate that it is not orthologous to the other Emx1 genes, and therefore, in vertebrates there must be three Emx genes. Alternatively, if the zebrafish emx1 gene is orthologous to the tetrapod one, it must have undergone to strong diversifying selection.