Metronomic chemotherapy (mCHT) in metastatic triple-negative breast cancer (TNBC) patients: results of the VICTOR-6 study.

PURPOSE: Triple-negative breast cancer (TNBC) represents a subtype of breast cancer which lacks the expression of oestrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor-2 (HER2): TNBC accounts for approximately 20% of newly diagnosed breast cancers and is associated with younger age at diagnosis, greater recurrence risk and shorter survival time. Therapeutic options are very scarce. Aim of the present analysis is to provide further insights into the clinical activity of metronomic chemotherapy (mCHT), in a real-life setting. METHODS: We used data included in the VICTOR-6 study for the present analysis. VICTOR-6 is an Italian multicentre retrospective cohort study, which collected data of metastatic breast cancer (MBC) patients who have received mCHT between 2011 and 2016. Amongst the 584 patients included in the study, 97 were triple negative. In 40.2% of the TNBC patients, mCHT was the first chemotherapy treatment, whereas 32.9% had received 2 or more lines of treatment for the metastatic disease. 45.4% out of 97 TNBC patients received a vinorelbine (VRL)-based regimen, which resulted in the most used type of mCHT, followed by cyclophosphamide (CTX)-based regimens (30.9%) and capecitabine (CAPE)-based combinations (22.7%). RESULTS: Overall response rate (ORR) and disease control rate (DCR) were 17.5% and 64.9%, respectively. Median progression free survival (PFS) and overall survival (OS) were 6.0 months (95% CI: 4.9-7.2) and 12.1 months (95% CI: 9.6-16.7). Median PFS was 6.9 months for CAPE-based regimens (95% CI: 5.0-18.4), 6.1 months (95% CI: 4.0-8.9) for CTX-based and 5.3 months (95% CI: 4.1-9.5) for VRL-based ones. Median OS was 18.2 months (95% CI: 9.1-NE) for CAPE-based regimens and 11.8 months for VRL- (95% CI: 9.3-16.7 and CTX-based ones (95%CI: 8.7-52.8). Tumour response, PFS and OS decreased proportionally in later lines. CONCLUSION: This analysis represents the largest series of TNBC patients treated with mCHT in a real-life setting and provides further insights into the advantages of using this strategy even in this poor prognosis subpopulation.

Targeted whole exome sequencing and Drosophila modelling to unveil the molecular basis of primary ovarian insufficiency.

STUDY QUESTION: Can a targeted whole exome sequencing (WES) on a cohort of women showing a primary ovarian insufficiency (POI) phenotype at a young age, combined with a study of copy number variations, identify variants in candidate genes confirming their deleterious effect on ovarian function? SUMMARY ANSWER: This integrated approach has proved effective in identifying novel candidate genes unveiling mechanisms involved in POI pathogenesis. WHAT IS KNOWN ALREADY: POI, a condition occurring in 1% of women under 40 years of age, affects women's fertility leading to a premature loss of ovarian reserve. The genetic causes of POI are highly heterogeneous and several determinants contributing to its prominent oligogenic inheritance pattern still need to be elucidated. STUDY DESIGN, SIZE, DURATION: WES screening for pathogenic variants of 41 Italian women with non-syndromic primary and early secondary amenorrhoea occurring before age 25 was replicated on another 60 POI patients, including 35 French and 25 American women, to reveal statistically significant shared variants. PARTICIPANTS/MATERIALS, SETTING, METHODS: The Italian POI patients' DNA were processed by targeted WES including 542 RefSeq genes expressed or functioning during distinct reproductive or ovarian processes (e.g. DNA repair, meiosis, oocyte maturation, folliculogenesis and menopause). Extremely rare variants were filtered and selected by means of a Fisher Exact test using several publicly available datasets. A case-control Burden test was applied to highlight the most significant genes using two ad-hoc control female cohorts. To support the obtained data, the identified genes were screened on a novel cohort of 60 Caucasian POI patients and the same case-control analysis was carried out. Comparative analysis of the human identified genes was performed on mouse and Drosophila melanogaster by analysing the orthologous genes in their ovarian phenotype, and two of the selected genes were fruit fly modelled to explore their role in fertility. MAIN RESULTS AND THE ROLE OF CHANCE: The filtering steps applied to search for extremely rare pathogenic variants in the Italian cohort revealed 64 validated single-nucleotide variants/Indels in 59 genes in 30 out of 41 screened women. Burden test analysis highlighted 13 ovarian genes as being the most enriched and significant. To validate these findings, filtering steps and Burden analysis on the second cohort of Caucasian patients yielded 11 significantly enriched genes. Among them, AFP, DMRT3, MOV10, FYN and MYC were significant in both patient cohorts and hence were considered strong candidates for POI. Mouse and Drosophila comparative analysis evaluated a conserved role through the evolution of several candidates, and functional studies using a Drosophila model, when applicable, supported the conserved role of the MOV10 armitage and DMRT3 dmrt93B orthologues in female fertility. LARGE SCALE DATA: The datasets for the Italian cohort generated during the current study are publicly available at ClinVar database (http://www.ncbi.nlm.nih.gov/clinvar/): accession numbers SCV001364312 to SCV001364375. LIMITATIONS, REASONS FOR CAUTION: This is a targeted WES analysis hunting variants in candidate genes previously identified by different genomic approaches. For most of the investigated sporadic cases, we could not track the parental inheritance, due to unavailability of the parents' DNA samples; in addition, we might have overlooked additional rare variants in novel candidate POI genes extracted from the exome data. On the contrary, we might have considered some inherited variants whose clinical significance is uncertain and might not be causative for the patients' phenotype. Additionally, as regards the Drosophila model, it will be extremely important in the future to have more mutants or RNAi strains available for each candidate gene in order to validate their role in POI pathogenesis. WIDER IMPLICATIONS OF THE FINDINGS: The genomic, statistical, comparative and functional approaches integrated in our study convincingly support the extremely heterogeneous oligogenic nature of POI, and confirm the maintenance across the evolution of some key genes safeguarding fertility and successful reproduction. Two principal classes of genes were identified: (i) genes primarily involved in meiosis, namely in synaptonemal complex formation, asymmetric division and oocyte maturation and (ii) genes safeguarding cell maintenance (piRNA and DNA repair pathways). STUDY FUNDING/COMPETING INTEREST(S): This work was supported by Italian Ministry of Health grants 'Ricerca Corrente' (08C621_2016 and 08C924_2019) provided to IRCCS Istituto Auxologico Italiano, and by 'Piano Sostegno alla Ricerca' (PSR2020_FINELLI_LINEA_B) provided by the University of Milan; M.P.B. was supported by Telethon-Italy (grant number GG14181). There are no conflicts of interest.

High-resolution array-CGH analysis on 46,XX patients affected by early onset primary ovarian insufficiency discloses new genes involved in ovarian function.

STUDY QUESTION: Can high resolution array-CGH analysis on a cohort of women showing a primary ovarian insufficiency (POI) phenotype in young age identify copy number variants (CNVs) with a deleterious effect on ovarian function? SUMMARY ANSWER: This approach has proved effective to clarify the role of CNVs in POI pathogenesis and to better unveil both novel candidate genes and pathogenic mechanisms. WHAT IS KNOWN ALREADY: POI describes the progression toward the cessation of ovarian function before the age of 40 years. Genetic causes are highly heterogeneous and despite several genes being associated with ovarian failure, most of genetic basis of POI still needs to be elucidated. STUDY DESIGN, SIZE, DURATION: The current study included 67 46,XX patients with early onset POI (<19 years) and 134 control females recruited between 2012 and 2016 at the Medical Cytogenetics and Molecular Genetics Lab, IRCCS Istituto Auxologico Italiano. PARTICIPANTS/MATERIALS, SETTING, METHODS: High resolution array-CGH analysis was carried out on POI patients' DNA. Results of patients and female controls were analyzed to search for rare CNVs. All variants were validated and subjected to a gene content analysis and disease gene prioritization based on the present literature to find out new ovary candidate genes. Case-control study with statistical analysis was carried out to validate our approach and evaluate any ovary CNVs/gene enrichment. Characterization of particular CNVs with molecular and functional studies was performed to assess their pathogenic involvement in POI. MAIN RESULTS AND THE ROLE OF CHANCE: We identified 37 ovary-related CNVs involving 44 genes with a role in ovary in 32 patients. All except one of the selected CNVs were not observed in the control group. Possible involvement of the CNVs in POI pathogenesis was further corroborated by a case-control analysis that showed a significant enrichment of ovary-related CNVs/genes in patients (P = 0.0132; P = 0.0126). Disease gene prioritization identified both previously reported POI genes (e.g. BMP15, DIAPH2, CPEB1, BNC1) and new candidates supported by transcript and functional studies, such as TP63 with a role in oocyte genomic integrity and VLDLR which is involved in steroidogenesis. LARGE SCALE DATA: ClinVar database (http://www.ncbi.nlm.nih.gov/clinvar/); accession numbers SCV000787656 to SCV000787743. LIMITATIONS, REASONS FOR CAUTION: This is a descriptive analysis for almost all of the CNVs identified. Inheritance studies of CNVs in some non-familial sporadic cases was not performed as the parents' DNA samples were not available. Addionally, RT-qPCR analyses were carried out in few cases as RNA samples were not always available and the genes were not expressed in blood. WIDER IMPLICATIONS OF THE FINDINGS: Our array-CGH screening turned out to be efficient in identifying different CNVs possibly implicated in disease onset, thus supporting the extremely wide genetic heterogeneity of POI. Since almost 50% of cases are negative rare ovary-related CNVs, array-CGH together with next generation sequencing might represent the most suitable approach to obtain a comprehensive genetic characterization of POI patients. STUDY FUNDING/COMPETING INTEREST(S): Supported by Italian Ministry of Health grants 'Ricerca Corrente' (08C203_2012) and 'Ricerca Finalizzata' (GR-2011-02351636, BIOEFFECT) to IRCCS Istituto Auxologico Italiano.

Identification of a novel X-linked gene responsible for Emery-Dreifuss muscular dystrophy.

Emery-Dreifuss muscular dystrophy (EDMD) is an X-linked recessive disorder characterized by slowly progressing contractures, wasting of skeletal muscle and cardiomyopathy. Heart block is a frequent cause of death. The disease gene has been mapped to distal Xq28. Among many genes in this region, we selected eight transcripts expressed at high levels in skeletal muscle, heart and/or brain as the best candidates for the disease. We now report, in all five patients studied, unique mutations in one of the genes, STA: these mutations result in the loss of all or part of the protein. The EDMD gene encodes a novel serine-rich protein termed emerin, which contains a 20 amino acid hydrophobic domain at the C terminus, similar to that described for many membrane proteins of the secretory pathway involved in vesicular transport.

A novel X-linked gene, G4.5. is responsible for Barth syndrome.

Barth syndrome is a severe inherited disorder, often fatal in childhood, characterized by cardiac and skeletal myopathy, short stature and neutropenia. The disease has been mapped to a very gene-rich region in distal portion of Xq28. We now report the identification of unique mutations in one of the genes in this region, termed G4.5, expressed at high level in cardiac and skeletal muscle. Different mRNAs can be produced by alternative splicing of the primary G4.5 transcript, encoding novel proteins that differ at the N terminus and in the central region. The mutations introduce stop codons in the open reading frame interrupting translation of most of the putative proteins (which we term 'tafazzins'). Our results suggest that G4.5 is the genetic locus responsible for the Barth syndrome.

Mutations in the gene encoding lamin A/C cause autosomal dominant Emery-Dreifuss muscular dystrophy.

Emery-Dreifuss muscular dystrophy (EDMD) is characterized by early contractures of elbows and Achilles tendons, slowly progressive muscle wasting and weakness, and a cardiomyopathy with conduction blocks which is life-threatening. Two modes of inheritance exist, X-linked (OMIM 310300) and autosomal dominant (EDMD-AD; OMIM 181350). EDMD-AD is clinically identical to the X-linked forms of the disease. Mutations in EMD, the gene encoding emerin, are responsible for the X-linked form. We have mapped the locus for EDMD-AD to an 8-cM interval on chromosome 1q11-q23 in a large French pedigree, and found that the EMD phenotype in four other small families was potentially linked to this locus. This region contains the lamin A/C gene (LMNA), a candidate gene encoding two proteins of the nuclear lamina, lamins A and C, produced by alternative splicing. We identified four mutations in LMNA that co-segregate with the disease phenotype in the five families: one nonsense mutation and three missense mutations. These results are the first identification of mutations in a component of the nuclear lamina as a cause of inherited muscle disorder. Together with mutations in EMD (refs 5,6), they underscore the potential importance of the nuclear envelope components in the pathogenesis of neuromuscular disorders.

Mutations in GDI1 are responsible for X-linked non-specific mental retardation.

Rab GDP-dissociation inhibitors (GDI) are evolutionarily conserved proteins that play an essential role in the recycling of Rab GTPases required for vesicular transport through the secretory pathway. We have found mutations in the GDI1 gene (which encodes uGDI) in two families affected with X-linked non-specific mental retardation. One of the mutations caused a non-conservative substitution (L92P) which reduced binding and recycling of RAB3A, the second was a null mutation. Our results show that both functional and developmental alterations in the neuron may account for the severe impairment of learning abilities as a consequence of mutations in GDI1, emphasizing its critical role in development of human intellectual and learning abilities.

Final results of the real-life observational VICTOR-6 study on metronomic chemotherapy in elderly metastatic breast cancer (MBC) patients.

Nowadays, treatment of metastatic breast cancer (MBC) has been enriched with novel therapeutical strategies. Metronomic chemotherapy (mCHT) is a continuous and frequent administration of chemotherapy at a lower dose and so whit less toxicity. Thus, this strategy could be attractive for elderly MBC patients. Aim of this analysis is to provide insights into mCHT's activity in a real-life setting of elderly MBC patients. Data of patients ≥ 75 years old included in VICTOR-6 study were analyzed. VICTOR-6 is a multicentre, Italian, retrospective study, which collected data on mCHT in MBC patients treated between 2011 and 2016. A total of 112 patients were included. At the beginning of mCHT, median age was 81 years (75-98) and in 33% of the patients mCHT was the first line choice. Overall Response Rate (ORR) and Disease Control Rate (DCR) were 27.9% and 79.3%, respectively. Median PFS ranged between 7.6 and 9.1 months, OS between 14.1 and 18.5 months. The most relevant toxicity was the hematological one (24.1%); severe toxicity (grade 3-4) ranged from 0.9% for skin toxicity up to 8% for hematologic one. This is a large study about mCHT in elderly MBC patients, providing insights to be further investigated in this subgroup of frail patients.

Hypoxic liver perfusion with mitomycin-C for treating multifocal metastases and unresectable primary tumours: a single-centre series of 42 patients.

PURPOSE: The purpose of our study was to retrospectively evaluate the feasibility, toxicity and impact on overall (OS) and disease-free (DFS) survival of intra-arterial liver perfusion with mitomycin-C (MMC) [hypoxic liver perfusion with MMC (HLPM)] in patients with multifocal liver metastases or with unresectable primary liver tumours. MATERIALS AND METHODS: Forty-two patients underwent 56 intra-arterial liver infusions with MMC between June 2001 and May 2009. The patients presented specific characteristics, i.e. they were all refractory to locoregional (LR) and/or systemic treatments. HLPM consists of selective catheterisation of the common hepatic artery, permanent occlusion of the gastroduodenal artery at its origin using metal coils, an inflated balloon catheter placement at the origin of the proper hepatic artery to block blood flow and induce hypoxia for around 10 min, MMC infusion and vascular-bed occlusion through injection of an absorbable haemostatic agent. During the procedure, the patients received anaesthesiological monitoring. Biochemical and morphological responses were evaluated, as were haematological, hepatic and systemic toxicity. RESULTS: Patients were hospitalised for 10 days on average (range 7-15). Side effects were liver toxicity in all cases, acute pancreatitis in one case and liver failure in one case. Computed tomography performed at 30 days documented a partial response (PR) in 29%, stable disease (SD) in 45% and progressive disease (PD) in 26% of patients. The response lasted 4 months on average (range 3-6). Mean overall survival (OS) was 20 months for all patients, reaching 30 months in those with colorectal carcinoma. CONCLUSIONS: The procedure is feasible, and treatmentrelated toxicity and mortality rates are acceptable. It may be considered a palliative treatment option in patients with advanced liver disease in centres with adequately experienced medical teams.

Normal serum concentrations of anti-Müllerian hormone in women with regular menstrual cycles.

Anti-Müllerian hormone (AMH) has become the 'molecule of the moment' in the field of reproductive endocrinology. Indeed, it is valuable as a means of increasing understanding of ovarian pathophysiology and for guiding clinical management across a broad range of conditions. However, no normative values have been established for circulating AMH in healthy women. In this cross-sectional study, 277 healthy females (aged 18-50 years) were included. AMH was measured by commercial enzyme-linked immunosorbent assay. Serum AMH concentrations show a progressive decline with female ageing. The age-related changes in AMH were best fitted by a polynomial function. Mean AMH concentrations were not modified by past use of oral contraceptive and were independent of parity of women. Age-specific normative values for circulating AMH concentration were established. AMH concentrations seem to be independent of the reproductive history of the patient.

Epigenetic analysis of the critical region I for premature ovarian failure: demonstration of a highly heterochromatic domain on the long arm of the mammalian X chromosome.

BACKGROUND: X chromosome rearrangements defined a critical region for premature ovarian failure (POF) that extended for >15 Mb in Xq. It has been shown previously that the region could be divided into two functionally distinct portions and suggested that balanced translocations interrupting its proximal part, critical region 1 (CR1), could be responsible for POF through downregulation of ovary expressed autosomal genes translocated to the X chromosome. RESULTS AND CONCLUSION: This study reports that such position effect can indeed be demonstrated by analysis of breakpoint regions in somatic cells of POF patients and by the finding that CR1 has a highly heterochromatic organisation, very different from that of the euchromatic autosomal regions involved in the rearrangements. The chromatin organisation of the POF CR1 is likely to be responsible for the epigenetic modifications observed in POF patients. The characteristics of CR1 and its downregulation in oocytes may very well explain its role in POF and the frequency of the POF phenotype in chromosomal rearrangements involving Xq. This study also demonstrates a large and evolutionary conserved domain of the long arm of the X chromosome, largely corresponding to CR1, that may have structural or functional roles, in oocyte maturation or in X chromosome inactivation.

Isolation of sequences that span the fragile X and identification of a fragile X-related CpG island.

Yeast artificial chromosomes (YACs) were obtained from a 550-kilobase region that contains three probes previously mapped as very close to the locus of the fragile X syndrome. These YACs spanned the fragile site in Xq27.3 as shown by fluorescent in situ hybridization. An internal 200-kilobase segment contained four chromosomal breakpoints generated by induction of fragile X expression. A single CpG island was identified in the cloned region between markers DXS463 and DXS465 that appears methylated in mentally retarded fragile X males, but not in nonexpressing male carriers of the mutation nor in normal males. This CpG island may indicate the presence of a gene involved in the clinical phenotype of the syndrome.

Metronomic chemotherapy for advanced breast cancer patients in the real world practice: Final results of the VICTOR-6 study.

Metronomic chemotherapy (mCHT) refers to the minimum biologically effective dose of a chemotherapy agent given as a continuous dosing regimen, with no prolonged drug-free breaks, that leads to antitumor activity. Aim of the present study is to describe the use of mCHT in a retrospective cohort of metastatic breast cancer (MBC) patients in order to collect data regarding the different types and regimens of drugs employed, their efficacy and safety. Between January 2011 and December 2016, data of 584 metastatic breast cancer patients treated with mCHT were collected. The use of VRL-based regimens increased during the time of observation (2011: 16.8% - 2016: 29.8%), as well as CTX-based ones (2011: 17.1% - 2016: 25.6%), whereas CAPE-based and MTX-based regimens remained stable. In the 1st-line setting, the highest ORR and DCR were observed for VRL-based regimens (single agent: 44% and 88%; combination: 36.7% and 82.4%, respectively). Assuming VRL-single agent as the referee treatment (median PFS: 7.2 months, 95% CI: 5.3-10.3), the longest median PFS were observed in VRL-combination regimens (9.5, 95%CI 88.8-11.3, HR = 0.72) and in CAPE-single agent (10.7, 95%CI 8.3-15.8, HR = 0.70). The VICTOR-6 study provides new data coming from the real-life setting, by adding new information regarding the use of mCHT as an option of treatment for MBC patients.

Muscular dystrophies: alterations in a limited number of cellular pathways?

Identification of new genes involved in muscle disorders has dramatically changed the traditional clinical classification of the large and heterogeneous group of the muscular dystrophies. Results obtained in recent years by positional candidate cloning have demonstrated the role of the sarcolemma and of the nuclear envelope in normal muscle function and have elucidated molecular pathways perturbed by mutations that lead to muscular dystrophy.

X-linked non-specific mental retardation.

Non-specific mental retardation is a very common and genetically heterogeneous disorder but, to date, only six genes related to this condition have been identified. Five of these six have been found in the past two years, through positional-cloning efforts of mapped X-linked families. The characteristics of the newly identified genes are providing insights into the molecular mechanisms of mental impairment and the development of cognitive functions.

Neurite extension occurs in the absence of regulated exocytosis in PC12 subclones.

We have investigated the process leading to differentiation of PC12 cells. This process is known to include extension of neurites and changes in the expression of subsets of proteins involved in cytoskeletal rearrangements or in neurosecretion. To this aim, we have studied a PC12 clone (trk-PC12) stably transfected with the nerve growth factor receptor TrkA. These cells are able to undergo both spontaneous and neurotrophin-induced morphological differentiation. However, both undifferentiated and nerve growth factor-differentiated trk-PC12 cells appear to be completely defective in the expression of proteins of the secretory apparatus, including proteins of synaptic vesicles and large dense-core granules, neurotransmitter transporters, and neurotransmitter-synthesizing enzymes. These results indicate that neurite extension can occur independently of the presence of the neurosecretory machinery, including the proteins that constitute the fusion machine, suggesting the existence of differential activation pathways for the two processes during neuronal differentiation. These findings have been confirmed in independent clones obtained from PC12-27, a previously characterized PC12 variant clone globally incompetent for regulated secretion. In contrast, the integrity of the Rab cycle appears to be necessary for neurite extension, because antisense oligonucleotides against the neurospecific isoform of Rab-guanosine diphosphate-dissociation inhibitor significantly interfere with process formation.

Automatic pedigree reconstruction for genetic studies in isolated populations.

This paper describes a tool implemented to automatically reconstruct the pedigree of an isolated population of Northern Italy with the aim of supporting genetic studies. The goal of such studies is to analyze genealogic, clinical and genetic data for genetic dissection of complex diseases. In this context the reconstruction of the population pedigree is fundamental to verify that such population is a genetic isolate and obtain the parental relationships among the individuals participating to the study. The algorithm presented in the paper, from heterogeneous data sources (demographic municipal and parish archives and other data sources), derives the pedigree applying several heuristic rules in a predefined order. One of the main difficulties in performing such task stands in the "record linkage" process that requires the definition of a sufficiently general strategy for managing the ambiguities caused by missing or imprecise/erroneous input data. The paper, finally, presents and discusses the preliminary results obtained by reconstructing the pedigree of four villages from the data collected during the first eighteen months of project.

Processing of ribosomal RNA in a temperature sensitive mutant of BHK cells.

The processing of ribosomal RNA has been studied in a temperature sensitive mutant of the Syrian hamster cell line BHK 21. At 39 degrees C, these cells are unable to synthesize 28S RNA, and 60S ribosomal subunits, while 18S RNA, and 40S subunits are produced at both temperatures. At 39 degrees C the 45S RNA precursor is transcribed and processed as in wild type cells. The processing of the RNA precursors becomes defective after the cleavage of the 41S RNA, and the separation of the 18S and 28S RNAs sequences in two different RNA molecules. The 36S RNA precursor, which is always present in very small quantity in the nucleoli of wild type cells and of the mutant at 33 degrees C, is found in very large amounts in the mutant at 39 degrees C. The 36S RNA can be, however, slowly processed to 32S RNA. The 32S RNA cannot be processed at 39 degrees C, and it is degraded soon after its formation. Only a small proportion accumulates in the nucleoli. The 32S RNA synthesized at 39 degrees C cannot be processed to 28S RNA upon shift to the permissive temperature, even when the processing of the newly synthesized rRNA has returned to normal. The data suggest that the 36S and 32S RNAs are contained in aberrant ribonucleoprotein particles, leading to a defective processing of the particles as a whole.

DNA variants in the human RAB3A gene are not associated with autism.

Mutation screening of the RAB3A gene in 47 individuals with autism provided no evidence that DNA variants in this gene are associated with autism. Since Rab3a constitutive knockout mice react to novel stimuli with hyperactivity, a further search for association of RAB3A DNA variants with other neurobehavioral disorders such as attention deficit/hyperactivity disorder appears justified.

The CpG island in the 5' region of the G6PD gene of man and mouse.

The nucleotide (nt) sequence of the entire CpG island in the 5' region of the human glucose-6-phosphate dehydrogenase-encoding gene (G6PD) and of the corresponding region in mouse was determined. In comparison to the human gene, the 5' region of the mouse G6PD gene has highly reduced G + C and CpG dinucleotide content, but maintains the functional features of a CpG island, as it is differentially methylated on the active vs. the inactive X chromosome. In addition to the expected conservation of exons, nt sequence comparison showed that several boxes are highly conserved between the two species in the 5' flanking DNA and in the first intron. Moreover, the conservation of the position of most CpG dinucleotides in the promoter region and in one of the upstream boxes, at about -900, gives support to the hypothesis that, in each island, specific CpGs play a major role in the regulation of gene expression.