Microbiology 2.0–A “behind the scenes” consideration for artificial intelligence applications for interpretive culture plate reading in routine diagnostic laboratories

Laboratory automation with Artificial Intelligence (AI) features have now emerged into routine diagnostic clinical use to interpret growth on agar plates. Applications are currently limited to urine samples and infection control screens, yet some of the details around the development of algorithms remain entrenched with AI development specialists and are not well understood by laboratorians. The generation of algorithms is not a trivial task and is a highly structured process, with several considerations needed to develop the appropriate data for specific intended uses. Understanding these considerations highlights the limitations of any algorithm created and informs better design practices so that algorithm objectives can be thoroughly tested prior to routine use.

P04.08 The role of SCN1A in glioblastomas and mixed neuronal glial tumors of pediatric age

BACKGROUND

Low and high grade gliomas, are the most common pediatric central nervous system (CNS) tumors and they show an extremely broad range of clinical behavior. Pediatric glioma is distinct from its adult counterpart with different genetic/epigenetic profile and biological features. Recently, several studies have shown the involvement of voltage-gated Na+ channels (VGSC) in different types of cancer, including gliomas. VGSC are multimeric transmembrane complexes, responsible for membrane depolarization in excitable cells playing an important role also in cell proliferation, migration, apoptosis and differentiation. VGSC are therapeutic targets in cardiovascular and neurological disorders and, in cancers, they could be a novel target for the development of promising anticancer therapy

MATERIAL AND METHODS

Firstly, we explored the genetic background of 9 pediatric glioblastomas (1–9 pGBMs), through whole-exome sequencing (WES) using HiSeq1000 platform (Illumina) with paired-end approach. On the basis of our results, we extended our study in another group of 16 epileptogenic mixed neuronal-glial tumors of pediatric age, (WHO grade I and II), through an amplicon approach (TSCA) using MiniSeq System platform (Illumina)

RESULTS

We identified variants in SCN1A gene in 3/9 pGBMs: case 3 had c.5782C>G in tumor and blood; case 5 showed c.2278G>T and two mosaic variants (c.5933C>T, 22% and c.4942C>T, 14%); case 6 showed c.667G>T variant only in tumor, and not in other non tumoral tissues (blood, urine and buccal swab). No variants in SCN1A were identified in a group of 16 pediatric mixed gliomas

CONCLUSION

In this study, we explore the genetic background of two groups of pediatric neuroepithelial brain tumors, through Next generation sequencing approach. We identified only in pGBMs variants in SCN1A gene that encoded for VGSCs and is involved in a spectrum of early-onset epileptic encephalopathies. None of our mutated patients showed history of epilepsy. Now, it is not clear the significance of these variants in pGBMs but interestingly, these variants are present in pGBM and not in mixed gliomas. Further studies on a big cohort of patients are needed to establish if they could play a role in pGBMs aggressiveness, migration and progression. Moreover, VGSCs could be a pharmacological target in pGBMs treatment

MicroRNA-551b expression profile in low and high-grade cervical intraepithelial neoplasia

OBJECTIVE

To evaluate the expression of microRNA (miR)-551b in patients with low and high grade cervical intraepithelial neoplasia (CIN) and to find an association with high-risk Human Papillomavirus (HR-HPV) infection-related prognostic biomarkers.

PATIENTS AND METHODS

The expression level of miR-551b was determined in 50 paraffin-embedded cervical specimens (10 normal squamous epithelium, 18 condylomas, 8 CIN1, and 14 CIN2-3) using quantitative Real-time polymerase chain reaction (qRT-PCR). χ2-test compared miR-551b expression in different diagnosis groups. An Ordered Logistic Regression and a Probit correlation were made to correlate miR-551b expression levels with the cervical tissue histological findings. The immunohistochemical distribution of p16 and Ki-67 according to histopathological findings was also assessed.

RESULTS

The distribution of the miR-551b expression profile was significantly lower in CIN1-3 samples compared to other histological diagnosis groups (condyloma and negative). The expression levels were inversely correlated to the cervical pathological grade, from negative to CIN2-3. A 1% increase in miR-551b expression level produced an increase of 19% to the probability of a minor histological grade diagnosis in a range from negative to CIN2-3 and an increase of 13% to the probability of a negative histological grade diagnosis. Among the cases with miR-551b expression < 0.02 (considered as cut-off value) a significant statistical correlation was found between p16 and Ki-67 expression and the diagnosis of CIN2-3.

CONCLUSIONS

Our data showed a significant inverse correlation between miR-551b expression and the histological grading of the lesions, suggesting a tumor suppressive function in the different stages of cervical dysplasia.

Diagnostic application of a capture based NGS test for the concurrent detection of variants in sequence and copy number as well as LOH

Whole exome sequencing (WES) has made the identification of causative SNVs/InDels associated with rare Mendelian conditions increasingly accessible. Incorporation of softwares allowing CNVs detection into the WES bioinformatics pipelines may increase the diagnostic yield. However, no standard protocols for this analysis are so far available and CNVs in non-coding regions are totally missed by WES, in spite of their possible role in the regulation of the flanking genes expression. So, in a number of cases the diagnostic workflow contemplates an initial investigation by genomic arrays followed, in the negative cases, by WES. The opposite workflow may also be applied, according to the familial segregation of the disease. We show preliminary results for a diagnostic application of a single next generation sequencing panel permitting the concurrent detection of LOH and variations in sequences and copy number. This approach allowed us to highlight compound heterozygosity for a CNV and a sequence variant in a number of cases, the duplication of a non-coding region responsible for sex reversal, and a whole-chromosome isodisomy causing reduction to homozygosity for a WFS1 variant. Moreover, the panel enabled us to detect deletions, duplications, and amplifications with sensitivity comparable to that of the most widely used array-CGH platforms.

MYOCLONIC ASTATIC EPILEPSY IN A PATIENT WITH A DE NOVO 4q21.22q21.23 MICRODUPLICATION

Myoclonicastatic epilepsy (MAE) is a rare form of symptomatic generalized epilepsy of uncertain etiology. To search the possible genetic basis of the disorder, here we investigate a 15 year-old patient with MAE, who is the only person presenting epilepsy in the family. High resolution array-CGH analysis was conducted on DNA extracted from peripheral blood of the patient and the parents. The copy number variant(s) (CNVs) identified were further confirmed by Fluorescent In Situ Hybridization (FISH). The array-CGH identified a de novo microduplication of about 778 Kb in the chromosome region 4q21.22-q21.23, involving 11 genes. This is the first report of a de novo CNV in MAE. The genes involved in the duplication are potential candidates that can be investigated in the future to determine their exact role in the etiopathogenesis of the disorder. However, we suggest performing microarray chromosomal analysis in patients with MAE, since rare de novo CNVs could be identified, and this is known to affect the diagnostic process and recurrence risk assessment.

Focal dysplasia of the cerebral cortex and infantile spasms associated with somatic 1q21.1-q44 duplication including the AKT3 gene

Somatic and germline duplications or activating mutations of AKT3 have been reported in patients with hemimegalencephaly and megalencephaly. We performed array comparative genomic hybridization on brain tissue and blood in 16 consecutive patients with symptomatic epilepsy due to focal or multilobar malformations of cortical development who underwent surgical treatment of epilepsy. One patient with infantile spasms and a dysplastic left frontal lobe harboured a somatic trisomy of the 1q21.1-q44 chromosomal region, encompassing the AKT3 gene, in the dysplastic brain tissue but not in blood and saliva. Histopathology revealed severe cortical dyslamination, a thin cortex in the premotor area with microgyri and microsulci, immature neurons with disoriented dendrites and areas of cortical heterotopia in the sub-cortical white matter. These cytoarchitectural changes are close to those defining type Ib focal cortical dysplasia. Immunohistochemistry in brain specimens showed hyperactivation of the PI3K/AKT/mTOR pathway. These findings indicate that AKT3 upregulation may cause focal malformations of cortical development. There appears to be an etiologic continuum between hemimegalencephaly and focal cortical dysplastic lesions. The extent of brain malformations due to AKT3 upregulation may be related to the embryonic stage when the post-zygotic gene alteration occurs.

Phenotypic heterogeneity and mutational spectrum in a cohort of 45 Italian males subjects with X-linked ectodermal dysplasia

Ectodermal dysplasias (EDs) are a group of genetic disorders characterized by the abnormal development of the ectodermal-derived structures. X-linked hypohidrotic ectodermal dysplasia, resulting from mutations in ED1 gene, is the most common form. The main purpose of this study was to characterize the phenotype spectrum in 45 males harboring ED1 mutations. The study showed that in addition to the involvement of the major ectodermal tissues, the majority of patients also have alterations of several minor ectodermal-derived structures. Characterizing the clinical spectrum resulting from ED1 gene mutations improves diagnosis and can direct clinical care.

Mycobacterium avium complex--the role of potable water in disease transmission

Mycobacterium avium complex (MAC) is a group of opportunistic pathogens of major public health concern. It is responsible for a wide spectrum of disease dependent on subspecies, route of infection and patients pre-existing conditions. Presently, there is limited research on the incidence of MAC infection that considers both pulmonary and other clinical manifestations. MAC has been isolated from various terrestrial and aquatic environments including natural waters, engineered water systems and soils. Identifying the specific environmental sources responsible for human infection is essential in minimizing disease prevalence. This paper reviews current literature and case studies regarding the wide spectrum of disease caused by MAC and the role of potable water in disease transmission. Potable water was recognized as a putative pathway for MAC infection. Contaminated potable water sources associated with human infection included warm water distribution systems, showers, faucets, household drinking water, swimming pools and hot tub spas. MAC can maintain long-term contamination of potable water sources through its high resistance to disinfectants, association with biofilms and intracellular parasitism of free-living protozoa. Further research is required to investigate the efficiency of water treatment processes against MAC and into construction and maintenance of warm water distribution systems and the role they play in MAC proliferation.

Fabry disease: polymorphic haplotypes and a novel missense mutation in the GLA gene

Fabry disease: polymorphic haplotypes and a novel missense mutation in the GLA gene. Fabry disease (FD) is an X-linked lysosomal storage disorder with a heterogeneous spectrum of clinical manifestations that are caused by the deficiency of α-galactosidase A (α-Gal-A) activity. Although useful for diagnosis in males, enzyme activity is not a reliable biochemical marker in heterozygous females due to random X-chromosome inactivation, thus rendering DNA sequencing of the α-Gal-A gene, alpha-galactosidase gene (GLA), the most reliable test for the confirmation of diagnosis in females. The spectrum of GLA mutations is highly heterogeneous. Many polymorphic GLA variants have been described, but it is unclear if haplotypes formed by combinations of such variants correlate with FD, thus complicating molecular diagnosis in females with normal α-Gal-A activity. We tested 67 female probands with clinical manifestations that may be associated with FD and 110 control males with normal α-Gal-A activity. Five different combinations of GLA polymorphic variants were identified in 14 of the 67 females, whereas clearcut pathogenetic alterations, p.Met51Ile and p.Met290Leu, were identified in two cases. The latter has not been reported so far, and both mutant forms were found to be responsive to the pharmacological chaperone deoxygalactonojirimycin (DGJ; migalastat hydrochloride). Analysis of the male control population, as well as male relatives of a suspected FD female proband, permitted the identification of seven different GLA gene haplotypes in strong linkage disequilibrium. The identification of haplotypes in control males provides evidence against their involvement in the development of FD phenotypic manifestations.

Biosynthesis of 2-methylisoborneol in cyanobacteria

The production of odiferous metabolites, such as 2-methlyisoborneol (MIB), is a major concern for water utilities worldwide. Although MIB has no known biological function, the presence of the earthy/musty taste and odor attributed to this compound result in the reporting of numerous complaints by consumers, which undermines water utility performance and the safe and adequate provision of potable waters. Cyanobacteria are the major producers of MIB in natural waters, by mechanisms that have heretofore remained largely unstudied. To investigate the fundamental biological mechanism of MIB biosynthesis in cyanobacteria, the genome of a MIB-producing Pseudanabaena limnetica was sequenced using Next Generation Sequencing, and the recombinant proteins derived from the putative MIB biosynthetic genes were biochemically characterized. We demonstrate that the biosynthesis of MIB in cyanobacteria is a result of 2 key reactions: 1) a S-adenosylmethionine-dependent methylation of the monoterpene precursor geranyl diphosphate (GPP) to 2-methyl-GPP catalyzed by geranyl diphosphate 2-methyltransferase (GPPMT) and 2) further cyclization of 2-methyl-GPP to MIB catalyzed by MIB synthase (MIBS) as part of a MIB operon. Based on a comparison of the component MIB biosynthetic genes in actinomycetes and cyanobacterial organisms, we hypothesize that there have been multiple rearrangements of the genes in this operon.

Regulation of MDM4 (MDMX) function by p76(MDM2): a new facet in the control of p53 activity

Under basal growth conditions, p53 function is tightly controlled by the members of MDM family, MDM2 and MDM4. The Mdm2 gene codes, in addition to the full-length p90(MDM2), for a short protein, p76(MDM2) that lacks the p53-binding domain. Despite this property and at variance with p90(MDM2), this protein acts positively toward p53, although the molecular mechanism remains elusive. Here, we report that p76(MDM2) antagonizes MDM4 inhibitory function. We show that p76(MDM2) possesses intrinsic ubiquitinating and degrading activity, and through these activities controls MDM4 levels. Furthermore, the presence of p76(MDM2) decreases the association of MDM4 with p53 and p90(MDM2), and antagonizes p53 degradation by the heterodimer MDM4/p90(MDM2). The p76(MDM2)-mediated regulation of MDM4 occurs in the cytoplasm, under basal growth conditions. Conversely, upon DNA damage, phosphorylation of MDM4Ser403 dissociates p76(MDM2) and prevents MDM4 degradation. The overall negative control of MDM4 by p76(MDM2) reflects on p53 function as p76(MDM2) impairs MDM4-mediated inhibition of p53 activity. In agreement with the positive role of p76(MDM2) toward p53, the p76(MDM2)/p90(MDM2) ratio significantly decreases in a group of thyroid tumor samples compared with normal counterparts. Overall, these findings reveal a new mechanism in the control of p53 basal activity that may account for the distinct sensitivity of tissues to stress signals depending on the balance among MDM proteins. Moreover, these data suggest an oncosuppressive function for a product of the Mdm2 gene.

Periventricular heterotopia, mental retardation, and epilepsy associated with 5q14.3-q15 deletion

BACKGROUND

Periventricular heterotopia (PH) is an etiologically heterogeneous disorder characterized by nodules of neurons ectopically placed along the lateral ventricles. Most affected patients have seizures and their cognitive level varies from normal to severely impaired. At present, two genes have been identified to cause PH when mutated. Mutations in FLNA (Xq28) and ARFGEF2 (20q13) are responsible for X-linked bilateral PH and a rare autosomal recessive form of PH with microcephaly. Chromosomal rearrangements involving the 1p36, 5p15, and 7q11 regions have also been reported in association with PH but the genes implicated remain unknown. Fourteen additional distinct anatomoclinical PH syndromes have been described, but no genetic insights into their causes have been gleaned.

METHODS

We report the clinical and imaging features of three unrelated patients with epilepsy, mental retardation, and bilateral PH in the walls of the temporal horns of the lateral ventricles, associated with a de novo deletion of the 5q14.3-15 region. We used microarray-based comparative genomic hybridization to define the boundaries of the deletions.

RESULTS

The three patients shared a common deleted region spanning 5.8 Mb and containing 14 candidate genes.

CONCLUSION

We identified a new syndrome featuring bilateral periventricular heterotopia (PH), mental retardation, and epilepsy, mapping to chromosome 5q14.3-q15. This observation reinforces the extreme clinical and genetic heterogeneity of PH. Array comparative genomic hybridization is a powerful diagnostic tool for characterizing causative chromosomal rearrangements of limited size, identifying potential candidate genes for, and improving genetic counseling in, malformations of cortical development.

[Tuberculosis-associated immune reconstitution inflammatory syndrome]

The prognosis of HIV-infected patients has dramatically improved since the advent of HAART. The immune recovery associated with HAART may result in immuno-pathological reactions and clinical deterioration when HAART is initiated in patients with tuberculosis (TB). This phenomenon is defined as immune reconstitution inflammatory syndrome (IRIS). In this review, we summarise the epidemiology, clinical presentations and management of TB-associated IRIS.

Evaluation of chromogenic technologies for use in Australian potable water

AIMS

To compare the use of MI agar, Membrane Lactose Glucoronide Agar (MLGA), CM1046 agar and Colilert-18 (Defined Substrate Technology, IDEXX Laboratories Pty. Ltd., Sydney) on Australian potable water.

METHODS AND RESULTS

Both potable (n = 369) and nonpotable waters (n = 35) were analysed by membrane filtration using chromogenic agars as well as Colilert-18 over a period of 12 months. Recoveries of stressed organisms on these chromogenic media were also investigated. Agar-based chromogenic technologies compared favourably to Colilert-18 for chlorinated waters, but there are possible limitations when using these agars for chloraminated waters. Additionally, the breakthrough of problematic organisms, especially oxidase positive organisms, may lead to misrepresentation or over-estimation of E. coli and total coliforms, particularly on MLGA and CM1046. The recovery of stressed organisms was favoured in the Colilert-18 system when compared to chromogenic agars.

CONCLUSIONS

MI agar performed better than the other chromogenic agars with respect to recovery and colour identification and discrimination of organisms, and compared favourably with Colilert-18. The use of chromogenic agars in chloraminated waters should be done cautiously.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study provides comparison data for laboratories looking to adopt chromogenic technologies, and is especially important for Australian laboratories wanting to uptake the use of MI agar (as used in USEPA method 1604) for routine use and for gaining accreditation. Additionally, to the best of our knowledge, this is the first reported evaluation of these agars in chloraminated waters and is especially timely as the use of this disinfection agent is increasing.

Development and field testing of a real-time PCR assay for cylindrospermopsin-producing cyanobacteria

AIMS

To develop and test a real-time PCR assay to detect and quantify genes specific to Cylindrospermopsis sp. and cylindrospermopsin-producing cyanobacteria.

METHOD AND RESULTS

A duplex real-time PCR assay was developed that targets a cylindrospermopsin-specific and Cylindrospermopsis raciborskii-specific DNA sequence. The C. raciborskii-specific sequence was based on the rpoC1 DNA-dependent RNA polymerase gene, whilst the cylindrospermopsin-specific sequence was selected by surveying an extensive number of potential cylindrospermopsin-producing cyanobacterial strains for genes implicated in toxin production, aoaA, aoaB and aoaC. In toxic strains, sequences of each of these three genes were always present; whilst in nontoxic strains the distribution of these sequences was patchy, resulting in what are likely to be natural deletion mutants. The real-time assay was optimized on a fixed and portable device, with results indicating that the reliable limit of detection for the assay was 100 copies per reaction or 1000 cells ml(-1) for both target sequences on both devices. In routine environmental samples enumerated by microscopy, the assay results were positive for all samples where C. raciborskii cells were observed at >1000 cells ml(-1) and negative in 15 samples where no C. raciborskii cells were observed. In field samples, the number of copies of the rpoC1 sequence more closely approximated the number of cells enumerated by microscopy, the number of copies of the pks sequence and detection of the toxin-specific sequence matched the results of toxin testing.

CONCLUSIONS

The duplex real-time PCR assay was a sensitive and rapid method for detecting potential cylindrospermopsin-producing cyanobacteria in the laboratory or in the field. The observation of probable natural deletion mutants provides further evidence that the aoaA, aoaB and aoaC genes are involved in toxin production.

SIGNIFICANCE AND IMPACT OF THE STUDY

This assay provides a new monitoring capability for tracking cylindrospermopsin-producing cyanobacteria that are an emerging threat to water quality.

Cryptic deletions are a common finding in "balanced" reciprocal and complex chromosome rearrangements: a study of 59 patients

Using array comparative genome hybridisation (CGH) 41 de novo reciprocal translocations and 18 de novo complex chromosome rearrangements (CCRs) were screened. All cases had been interpreted as "balanced" by conventional cytogenetics. In all, 27 cases of reciprocal translocations were detected in patients with an abnormal phenotype, and after array CGH analysis, 11 were found to be unbalanced. Thus 40% (11 of 27) of patients with a "chromosomal phenotype" and an apparently balanced translocation were in fact unbalanced, and 18% (5 of 27) of the reciprocal translocations were instead complex rearrangements with >3 breakpoints. Fourteen fetuses with de novo, apparently balanced translocations, all but two with normal ultrasound findings, were also analysed and all were found to be normal using array CGH. Thirteen CCRs were detected in patients with abnormal phenotypes, two in women who had experienced repeated spontaneous abortions and three in fetuses. Sixteen patients were found to have unbalanced mutations, with up to 4 deletions. These results suggest that genome-wide array CGH may be advisable in all carriers of "balanced" CCRs. The parental origin of the deletions was investigated in 5 reciprocal translocations and 11 CCRs; all were found to be paternal. Using customized platforms in seven cases of CCRs, the deletion breakpoints were narrowed down to regions of a few hundred base pairs in length. No susceptibility motifs were associated with the imbalances. These results show that the phenotypic abnormalities of apparently balanced de novo CCRs are mainly due to cryptic deletions and that spermatogenesis is more prone to generate multiple chaotic chromosome imbalances and reciprocal translocations than oogenesis.

De novo double translocation 3;13 and 4;8;18 in a patient with mental retardation and skeletal abnormalities

A de novo, apparently balanced complex chromosome rearrangement (CCR) involving five chromosomes and six chromosome breakpoints was found in a child with Marfanoid habitus, kyphoscoliosis, axillary pterygium, camptodactyly, joint laxity, and mild mental retardation. Fluorescence in situ hybridization (FISH) revealed a simple translocation involving chromosomes 3 and 13, and a complex rearrangement involving chromosomes 4, 8, and 18 with four breakpoints.

[Infective endocarditis: a retrospective analysis of inpatient cases]

The authors analysed retrospectively the clinical and laboratory features of patients hospitalised in a unit of infectious diseases in the period from 1996-99. In particular, the etiology, the antimicrobial susceptibility of responsible microorganisms, criteria utilized for diagnosis, antibiotic courses and outcomes were evaluated and discussed. Echocardiography is an essential tool in the diagnosis. Infective endocarditis remains a serious infection and is still associated with high morbidity and mortality rate, despite appropriate treatment. Seriously ill patients may require prompt surgery.

Inv dup del (1)(pter-->q44::q44-->q42:) with the classical phenotype of trisomy 1q42-qter

We report on a girl with a trisomy 1q42-q44 due to an inverted duplication of this region, associated with a terminal deletion of the long arm of the rearranged chromosome 1. Both the large duplication (more than 30 cM) and the small deletion were detected by FISH. Complete karyotype was: (46,XX, inv dup(1)(q44q42).ish(dup del 1)(q44q42)(D1S446x2, D1S423x2, tel1q-). The phenotype of the patient is characterized by macrocephaly with prominent forehead, downslanting palpebral fissures, micrognathia, and psychomotor retardation. All these clinical features are the same as observed for the typical trisomy 1q42-qter syndrome. The phenotypic effects of the inversion and the terminal deletion of 1q in addition to the trisomy are discussed here.

New syndrome of mental retardation, Robin sequence, and brachydactyly

We report on two sibs, brother and sister, affected with a multiple congenital anomalies/mental retardation (MCA/MR) syndrome, characterized by mild to moderate psychomotor delay, Robin sequence, peculiar facial appearance, and brachydactyly. To our knowledge, this combination of anomalies has not been reported previously. The occurrence of a similar pattern of anomalies in brother and sister suggests autosomal recessive inheritance; however, dominant transmission with reduced penetrance cannot be ruled out in our patients, since minor clinical signs, such as brachydactyly, are also present in the father.

Olfactory receptor-gene clusters, genomic-inversion polymorphisms, and common chromosome rearrangements

The olfactory receptor (OR)-gene superfamily is the largest in the mammalian genome. Several of the human OR genes appear in clusters with > or = 10 members located on almost all human chromosomes, and some chromosomes contain more than one cluster. We demonstrate, by experimental and in silico data, that unequal crossovers between two OR gene clusters in 8p are responsible for the formation of three recurrent chromosome macrorearrangements and a submicroscopic inversion polymorphism. The first two macrorearrangements are the inverted duplication of 8p, inv dup(8p), which is associated with a distinct phenotype, and a supernumerary marker chromosome, +der(8)(8p23.1pter), which is also a recurrent rearrangement and is associated with minor anomalies. We demonstrate that it is the reciprocal of the inv dup(8p). The third macrorearrangment is a recurrent 8p23 interstitial deletion associated with heart defect. Since inv dup(8p)s originate consistently in maternal meiosis, we investigated the maternal chromosomes 8 in eight mothers of subjects with inv dup(8p) and in the mother of one subject with +der(8), by means of probes included between the two 8p-OR gene clusters. All the mothers were heterozygous for an 8p submicroscopic inversion that was delimited by the 8p-OR gene clusters and was present, in heterozygous state, in 26% of a population of European descent. Thus, inversion heterozygosity may cause susceptibility to unequal recombination, leading to the formation of the inv dup(8p) or to its reciprocal product, the +der(8p). After the Yp inversion polymorphism, which is the preferential background for the PRKX/PRKY translocation in XX males and XY females, the OR-8p inversion is the second genomic polymorphism that confers susceptibility to the formation of common chromosome rearrangements. Accordingly, it may be possible to develop a profile of the individual risk of having progeny with chromosome rearrangements.

CENP-G in neocentromeres and inactive centromeres

CENP-G is a novel constitutive centromere-specific protein localized to the kinetochore inner plate and subjacent region. It has been identified as associating specifically with the alpha-1 subfamily of alpha-satellite DNA. In the present work, the localization of CENP-G was compared with that of other CENPs by immunofluorescence and fluorescence in situ hybridization. Studies were carried out on four abnormal human centromeres: two neocentromeres and two inactive centromeres. CENP-G was detected in one of the two inactive centromeres but not in the other that shows a partial deletion of the alphoid DNA. Interestingly, CENP-G is also present in neocentromeres, which lack alphoid DNA sequences, and in the human Y chromosome, which lacks the alpha-1 type of satellite DNA. These data provide further evidence that CENP-G may be an essential factor in centromeric function and that in centromeres lacking the alpha-1 subfamily of alphoid DNA, other DNA sequences are able to bind CENP-G.

Translocation (8;16) in a patient with acute myelomonocytic leukemia, occurring after treatment with fludarabine for a low-grade non-Hodgkin's lymphoma

We describe a 65-year old woman who developed a t(8;16)(p11;p13) positive acute myeloid leukemia (AML)-M4 without a prior myelodysplasia thirty-six months after a low-grade non-Hodgkin's lymphoma treated with alkylating agents (chlorambucil and cyclophosphamide) and fludarabine, a purine analog with a significant activity in lymphoproliferative disorders. The t(8;16)(p11;p13) is present in 0.4% of AML of M4-M5 cytotype. In the present case it was identified by conventional cytogenetics; involvement of the MOZ and CBP genes was demonstrated by fluorescence in situ hybridization, but not by reverse transcription polymerase chain reaction. The patient died of sepsis after the first course of induction chemotherapy. This is the first t(8;16) AML-M4 arising after fludarabine treatment of which the leukemogenic role in our case is very difficult to ascertain. Most t(8;16) t-AML cases had received anthracyclines with or without cyclophosphamide; none was ever administered chlorambucil. Our patient was never given anthracyclines and the cumulative doses of chlorambucil and cyclophosphamide employed were low.