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Recombinant DNA technologies of the current era, most of which are comparable to past works of science fiction, have had diverse and significant impacts on social life. Among them, genetic sequencing deserves particular attention. The widespread use of genetic testing has raised numerous concerns regarding autonomy, confidentiality and privacy. In this context, the proliferation of 'gene for X' reports influences debates about the potentially beneficial or detrimental uses of genetics. While several studies have reported concerns related to the collection, storage and use of genetic data, few have considered the technical shortcomings that can affect the reliability of interpretation of sequencing data. In this essay, we will cover some of the current practices of genetic testing and safety aspects of DNA data. To evaluate the reliability of DNA data we will raise the question whether an 'overestimation' of researchers' results might reflect an 'underestimation' of our genetic make-up in terms of the limitations of the parameters necessary for the correct interpretation of genomic DNA. Following that question we will highlight the responsibility of researchers for proper science communication to avoid misleading information about genetic sequencing data., Competing Interests: Declaration of competing interest The author declares that they have no conflict of interest., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Ribosome biogenesis requires prodigious transcriptional output in rapidly growing yeast cells and is highly regulated in response to both growth and stress signals. This minireview focuses on recent developments in our understanding of this regulatory process, with an emphasis on the 138 ribosomal protein genes (RPGs) themselves and a group of >200 ribosome biogenesis (RiBi) genes whose products contribute to assembly but are not part of the ribosome. Expression of most RPGs depends upon Rap1, a pioneer transcription factor (TF) required for the binding of a pair of RPG-specific TFs called Fhl1 and Ifh1. RPG expression is correlated with Ifh1 promoter binding, whereas Rap1 and Fhl1 remain promoter-associated upon stress-induced down regulation. A TF called Sfp1 has also been implicated in RPG regulation, though recent work reveals that its primary function is in activation of RiBi and other growth-related genes. Sfp1 plays an important regulatory role at a small number of RPGs where Rap1-Fhl1-Ifh1 action is subsidiary or non-existent. In addition, nearly half of all RPGs are bound by Hmo1, which either stabilizes or re-configures Fhl1-Ifh1 binding. Recent studies identified the proline rotamase Fpr1, known primarily for its role in rapamycin-mediated inhibition of the TORC1 kinase, as an additional TF at RPG promoters. Fpr1 also affects Fhl1-Ifh1 binding, either independently or in cooperation with Hmo1. Finally, a major recent development was the discovery of a protein homeostasis mechanism driven by unassembled ribosomal proteins, referred to as the Ribosome Assembly Stress Response (RASTR), that controls RPG transcription through the reversible condensation of Ifh1., (© 2021 The Author(s).)

While expression of ribosomal protein genes (RPGs) in the budding yeast has been extensively studied, a longstanding enigma persists regarding their co-regulation under fluctuating growth conditions. Most RPG promoters display one of two distinct arrangements of a core set of transcription factors (TFs) and are further differentiated by the presence or absence of the HMGB protein Hmo1. However, a third group of promoters appears not to be bound by any of these proteins, raising the question of how the whole suite of genes is co-regulated. We demonstrate here that all RPGs are regulated by two distinct, but complementary mechanisms driven by the TFs Ifh1 and Sfp1, both of which are required for maximal expression in optimal conditions and coordinated downregulation upon stress. At the majority of RPG promoters, Ifh1-dependent regulation predominates, whereas Sfp1 plays the major role at all other genes. We also uncovered an unexpected protein homeostasis-dependent binding property of Hmo1 at RPG promoters. Finally, we show that the Ifh1 paralog Crf1, previously described as a transcriptional repressor, can act as a constitutive RPG activator. Our study provides a more complete picture of RPG regulation and may serve as a paradigm for unravelling RPG regulation in multicellular eukaryotes., (© The Author(s) 2020. Published by Oxford University Press on behalf of Nucleic Acids Research.)

Background: DNA topoisomerase and telomerase enzymes are popular targets of several anti-tumor drugs. Smooth proceeding of telomeric recombination requires Topoisomerase II (Top2), which is involved in telomere-telomere recombination through functioning in relaxation of positive supercoils among the cells adopting telomerase-independent Alternative lengthening of telomere (ALT) pathway. Most of the inhibitors reported so far have been designed to targetsolely telomerase-positive cells, which can potentially lead to therapeutic failure because tumor cells treated with telomerase inhibitors can activate the ALT pathway for telomere maintenance. Knowing that ALT cells are more sensitive against a Top2 inhibitor, ICRF-93 agent, compared to telomerase-positive cells, we analyzed two selected ellipticine derivatives that we recently reported as TopII-targeting compounds, to assess their effects on the formation of DNA breaks and suppression of ALT pathway., Methods: Cell viability, Comet, C-Circle assays, dot blot, immunofluorescence staining, and telomere fluorescence in situ hybridization (FISH) staining were used for determining the effect of the compounds on ALT status of tumor cells., Results and Conclusions: Treatment of ALT cells with ellipticine derivatives resulted in the formation of DNA breaks and suppression of ALT-associated phenotypes in vitro. Our results will contribute to the development of therapeutic strategies combining telomerase and ALT pathway inhibitors.

Pioneer transcription factors (pTFs) bind to target sites within compact chromatin, initiating chromatin remodeling and controlling the recruitment of downstream factors. The mechanisms by which pTFs overcome the chromatin barrier are not well understood. Here, we reveal, using single-molecule fluorescence, how the yeast transcription factor Rap1 invades and remodels chromatin. Using a reconstituted chromatin system replicating yeast promoter architecture, we demonstrate that Rap1 can bind nucleosomal DNA within a chromatin fiber but with shortened dwell times compared to naked DNA. Moreover, we show that Rap1 binding opens chromatin fiber structure by inhibiting inter-nucleosome contacts. Finally, we reveal that Rap1 collaborates with the chromatin remodeler RSC to displace promoter nucleosomes, paving the way for long-lived bound states on newly exposed DNA. Together, our results provide a mechanistic view of how Rap1 gains access and opens chromatin, thereby establishing an active promoter architecture and controlling gene expression., Competing Interests: Declaration of Interests The authors declare no competing interests., (Copyright © 2019 The Author(s). Published by Elsevier Inc. All rights reserved.)

General Control Non-derepressible 5 (GCN5) and Alteration/Deficiency in Activation 2 and 3 proteins (ADA2 and ADA3, respectively) are subunits of the Histone AcetylTransferase (HAT) module of SAGA- and ATAC-type co-activators. We previously reported four new interacting partners of human ADA3 identified by screening a human fetal brain cDNA library using yeast two hybrid technology. One of these partners was Apoptosis-Antagonizing Transcription Factor (AATF), also known as Che-1, an RNA polymerase II-binding protein with a number of roles in different cellular processes including regulation of transcription, cell proliferation, cell cycle control, DNA damage responses and apoptosis. Che-1/AATF is a potential therapeutic target for cancer treatments. In this study, we aimed to identify whether besides ADA3, other components of the HAT modules of SAGA and ATAC complexes, human ADA2 and GCN5 also interact with Che-1/AATF. Co-immunoprecipitation and co-localization experiments were used to demonstrate association of AATF both with two ADA2 isoforms, ADA2A and ADA2B and with GCN5 proteins in human cells and yeast two-hybrid assays to delineate domains in the ADA2 and GCN5 proteins required for these interactions. These findings provide new insights into the pathways regulated by ADA-containing protein complexes.

Ellipticine (5,11-dimethyl-6H-pyrido[4,3-b]carbazole) is an antineoplastic agent that intercalates into DNA and alters topoisomerase II activity. Unfortunately, this compound displays a number of adverse properties. Therefore, to investigate new ellipticine-based compounds for their potential as topoisomerase II-targeted drugs, we synthesized two novel derivatives, N-methyl-5-demethyl ellipticine (ET-1) and 2-methyl-N-methyl-5-demethyl ellipticinium iodide (ET-2). As determined by DNA decatenation and cleavage assays, ET-1 and ET-2 act as catalytic inhibitors of human topoisomerase IIα and are both more potent than the parent compound. Neither compound impairs the ability of the type II enzyme to bind its DNA substrate. Finally, the potency of ET-1 and ET-2 as catalytic inhibitors of topoisomerase IIα appears to be related to their ability to intercalate into the double helix., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Two metabolites from the ascomycete fungus Septofusidium berolinense were recently identified as having antineoplastic activity [Ekiz et al. (2015) J. Antibiot. , DOI: 10.1038/ja.2015.84]. However, the basis for this activity is not known. One of the compounds [3,6-dihydroxy-2-propylbenzaldehyde (GE-1)] is a hydroquinone, and the other [2-hydroxymethyl-3-propylcyclohexa-2,5-diene-1,4-dione (GE-2)] is a quinone. Because some hydroquinones and quinones act as topoisomerase II poisons, the effects of GE-1 and GE-2 on DNA cleavage mediated by human topoisomerase IIα were assessed. GE-2 enhanced DNA cleavage ∼4-fold and induced scission with a site specificity similar to that of the anticancer drug etoposide. Similar to other quinone-based topoisomerase II poisons, GE-2 displayed several hallmark characteristics of covalent topoisomerase II poisons, including (1) the inability to poison a topoisomerase IIα construct that lacks the N-terminal domain, (2) the inhibition of DNA cleavage when the compound was incubated with the enzyme prior to the addition of plasmid, and (3) the loss of poisoning activity in the presence of a reducing agent. In contrast to GE-2, GE-1 did not enhance DNA cleavage mediated by topoisomerase IIα except at very high concentrations. However, the activity and potency of the metabolite were dramatically enhanced under oxidizing conditions. These results suggest that topoisomerase IIα may play a role in mediating the cytotoxic effects of these fungal metabolites.

Two large phosphatidylinositol 3-kinase-related protein kinases (PIKKs), ATM and ATR, play a central role in the DNA damage response pathway. PIKKs contain a highly conserved extreme C-terminus called the FRAP-ATM-TRRAP-C-terminal (FATC) domain. In budding yeast, ATM and ATR correspond to Tel1 and Mec1, respectively. In this study, we characterized functions of the FATC domain of Tel1 by introducing substitution or truncation mutations. One substitution mutation, termed tel1-21, and a truncation mutation, called tel1-ΔC, did not significantly affect the expression level. The tel1-21 mutation impaired the cellular response to DNA damage and conferred moderate telomere maintenance defect. In contrast, the tel1-ΔC mutation behaved like a null mutation, conferring defects in both DNA damage response and telomere maintenance. Tel1-21 protein localized to DNA ends as effectively as wild-type Tel1 protein, whereas Tel1-ΔC protein failed. Introduction of a hyperactive TEL1-hy mutation suppressed the tel1-21 mutation but not the tel1-ΔC mutation. In vitro analyses revealed that both Tel1-21 and Tel1-ΔC proteins undergo efficient autophosphorylation but exhibit decreased kinase activities toward the exogenous substrate protein, Rad53. Our results show that the FATC domain of Tel1 mediates localization to DNA ends and contributes to phosphorylation of target proteins., (© 2015 Ogi, Goto, Ghosh, et al. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).)

Telomeres, the ends of linear eukaryotic chromosomes, have a specialized chromatin structure that provides a stable chromosomal terminus. In budding yeast Rap1 protein binds to telomeric TG repeat and negatively regulates telomere length. Here we show that binding of multiple Rap1 proteins stimulates DNA double-stranded break (DSB) induction at both telomeric and non-telomeric regions. Consistent with the role of DSB induction, Rap1 stimulates nearby recombination events in a dosage-dependent manner. Rap1 recruits Rif1 and Rif2 to telomeres, but neither Rif1 nor Rif2 is required for DSB induction. Rap1-mediated DSB induction involves replication fork progression but inactivation of checkpoint kinase Mec1 does not affect DSB induction. Rap1 tethering shortens artificially elongated telomeres in parallel with telomerase inhibition, and this telomere shortening does not require homologous recombination. These results suggest that Rap1 contributes to telomere homeostasis by promoting chromosome breakage.

Background: Myeloid differentiation primary response 88 (MYD88) is a common adaptor protein that is responsible for signaling from several receptors; mutations in this gene may play a role in the pathogenesis of lymphoma., Aim: We aimed to determine the MYD88 L265P mutation frequency, the level of MYD88 expression, and their associations with clinicopathological parameters in mature B-cell non-Hodgkin lymphomas (NHLs)., Methods: A total of 68 patients were included in the study. The presence of the MYD88 L265P mutation was analyzed by real-time polymerase chain reaction and direct sequencing. MYD88 protein expression was evaluated by immunohistochemistry (IHC) using two different scoring systems., Results: MYD88 L265P mutation was present in eight (18.6%) diffuse large B-cell lymphoma (DLBCL) patients. We also observed a significant association between the loss of MYD88 expression and advanced stage in both mature B-cell NHL and DLBCL according to the first IHC scoring systems (p=0.015 and p=0.024, respectively). An association was also seen between MYD88 overexpression and low clinical risk in both mature B-cell NHL and DLBCL according to the second IHC scoring system (p=0.027 and p=0.024, respectively)., Conclusions: The L265P mutation may be helpful for understanding the pathogenesis of immune-privileged site-associated DLBCLs. The presence of the mutation, together with its protein overexpression, could also be used as a prognostic marker in advanced stage DLBCLs.

A considerable number of agents with chemotherapeutic potentials reported over the past years were shown to interfere with the reactions of DNA topoisomerases, the essential enzymes that regulate conformational changes in DNA topology. Gossypol, a naturally occurring bioactive phytochemical is a chemopreventive agent against various types of cancer cell growth with a reported activity on mammalian topoisomerase II. The compounds targeting topoisomerases vary in their mode of action; class I compounds act by stabilizing covalent topoisomerase-DNA complexes resulting in DNA strand breaks while class II compounds interfere with the catalytic function of topoisomerases without generating strand breaks. In this study, we report Gossypol as the interfering agent with type I topoisomerases as well. We also carried out an extensive set of assays to analyze the type of interference manifested by Gossypol on DNA topoisomerases. Our results strongly suggest that Gossypol is a potential class II inhibitor as it blocked DNA topoisomerase reactions with no consequently formed strand breaks.

ADA (alteration/deficiency in activation) 3 is a conserved component of several transcriptional adaptor and HAT (histone acetyltransferase) complexes that regulate RNA polymerase II-mediated gene expression. Within the HAT complexes ADA3 is associated with ADA2 and the HAT GCN5 (general control non-repressed 5). ADA3 plays roles in diverse cellular processes and also in malignancies by modulating GCN5 catalytic activity and/or by interactions with other regulators. To gain a better understanding of ADA3 function, we used a yeast two-hybrid approach to screen a human fetal cDNA library for proteins that interacted with hADA3 (human ADA3). We identified three novel hADA3-interacting partners, a transcriptional regulator, AATF (apoptosis-antagonizing transcription factor), and regulatory subunits of the PP1 (protein phosphatase 1) and PP2A (protein phosphatase 2A) [PPP1R7 (PP1 regulatory subunit 7) and PPP2R5D (PP2A 56 kDa regulatory subunit δ isoform) respectively]. Analysis of truncated versions of hADA3 indicated that the C-terminal ADA2-interacting domain was not required for these interactions. Fluorescent microscopy analysis and co-immunoprecipitation provided support for the co-localization and interaction of hADA3 with these proteins in human cells. Expression of the interacting proteins altered expression of an hADA3-regulated reporter gene, suggesting functional consequences for the interactions. The detected interactions of hADA3 might extend the spectrum of mechanisms by which ADA3 can contribute to the regulation of gene expression and shed light on processes mediated by these newly identified ADA3 partners.

Despite inherent limitations, the ease and rapidity of their use make transiently expressed reporter gene assays the most frequently used techniques for analyzing promoters and transcriptional regulators. The results of transient reporter gene assays are generally accepted to reflect transcriptional processes correctly, though these assays study regulatory sequences outside of the chromosomal environment and draw conclusions on transcription based on enzyme activity determination. For transient reporter gene assays, often more than one promoter is introduced into one cell. In addition to the one driving the primary reporter gene expression, a further one might serve to ensure the production of an internal control second reporter or/and a trans-acting factor. We demonstrate here by various examples that interference between physically unlinked promoters can profoundly affect reporter expression. Results of reporter gene assays performed by combinations of the cytomegalovirus promoter and various other promoter constructs (human immunodeficiency virus [HIV], Human T-cell Leukemia Virus Type I (HTLV-I), NF-κB-responsive, and p53-responsive) and trans-activator factors (HIV-Tat and p53) in different host cell lines (U2OS, HeLa, and L929) prove that interference between active transcription units can modify transcription responses dramatically. Since the interference depends on the promoters used, on the amount of transfected DNA, on the host cells, and on other factors, extra caution is required in interpreting results of transient reporter gene assays.

The vast majority of physiological processes in living cells are mediated by protein-protein interactions often specified by particular protein sequence motifs. PDZ domains, composed of 80-100 amino acid residues, are an important class of interaction motif. Among the PDZ-containing proteins, glutaminase interacting protein (GIP), also known as Tax Interacting Protein TIP-1, is unique in being composed almost exclusively of a single PDZ domain. GIP has important roles in cellular signaling, protein scaffolding and modulation of tumor growth and interacts with a number of physiological partner proteins, including Glutaminase L, β-Catenin, FAS, HTLV-1 Tax, HPV16 E6, Rhotekin and Kir 2.3. To identify the network of proteins that interact with GIP, a human fetal brain cDNA library was screened using a yeast two-hybrid assay with GIP as bait. We identified brain-specific angiogenesis inhibitor 2 (BAI2), a member of the adhesion-G protein-coupled receptors (GPCRs), as a new partner of GIP. BAI2 is expressed primarily in neurons, further expanding GIP cellular functions. The interaction between GIP and the carboxy-terminus of BAI2 was characterized using fluorescence, circular dichroism (CD) and nuclear magnetic resonance (NMR) spectroscopy assays. These biophysical analyses support the interaction identified in the yeast two-hybrid assay. This is the first study reporting BAI2 as an interaction partner of GIP., (Copyright © 2011 Elsevier Inc. All rights reserved.)

We investigated the effect of extremely low-frequency electromagnetic field (ELF-EMF) with pulse trains exposure on lipid peroxidation, and, hence, oxidative stress in the rat liver tissue. The parameters that we measured were the levels of plasma alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase as well as plasma albumin, bilirubin, and total protein levels in 30 adult male Wistar rats exposed to ELF. We also determined the percentage of apoptotic and necrotic cells of the kidney extracts from the animals by flow cytometry method. Apoptotic cell death was further characterized by monitoring DNA degradation using gel electrophoresis. The results showed an increase in the levels of oxidative stress indicators, and the flow cytometric data suggested a possible relationship between the exposure to magnetic field and the cell death. We showed significantly lower necrotic cell percentages in experimental animals compared to either unexposed or sham control groups. However, DNA ladder analyses did not differentiate between the groups. Our results were discussed in relation to the response of biological systems to EMF.

Background/aims: Human Cytochrome P450 (CYP) comprises a multigene family of microsomal enzymes that metabolize a wide variety of xenobiotics, including drugs and carcinogens. Although the a number of CYP enzymes were also detected in epithelial cells along the gastrointestinal tract, little is known about the expression of CYP genes in gastric tissue., Methodology: In this study, the expression patterns of CYP isoforms was investigated in a total of 14 antral biopsy tissues obtained from the patients with either chronic gastritis (n = 6) or cancer (n = 8) by gene-specific real-time reverse transcriptase -PCR analyses. We employed primer sets specific for CYPs -1A1, -1A2, -2A6, -2B6, -2C, -2D6, -2E1, and -3A5., Results: Among the isoforms CYP1A1, CYP2C and CYP2D6 gave rise to detectable mRNAs in all 14 gastric tissues while the mRNAs for the other CYPs were detected in some of the tissues. The expression patterns were compared to clinical parameters. There were no significant differences in the parameters between the two groups; however the mRNA expression of CYP2A6 was significantly higher in women than man (p < 0.05)., Conclusions: Our data suggests that the CYP isoforms were independently expressed with respect to the pathological status in human gastric tissue.

Chalcones (1,3-diaryl-2-propen-1-ones) are alpha, beta-unsaturated ketones with cytotoxic and anticancer properties. Several reports have shown that compounds with cytotoxic properties may also interfere with DNA topoisomerase functions. Five derivatives of 4'-hydroxychalcones were examined for cytotoxicity against transformed human T (Jurkat) cells as well as plasmid supercoil relaxation experiments using mammalian DNA topoisomerase I. The compounds were 3-phenyl-1-(4'-hydroxyphenyl)-2-propen-1-one (I), 3-(p-methylphenyl)-1-(4'-hydroxyphenyl)-2-propen-1-one (II), 3-(p-methoxyphenyl)-1-(4'-hydroxyphenyl)-2-propen-1-one (III), 3-(p-chlorophenyl)-1-(4'-hydroxyphenyl)-2-propen-1-one (IV), and 3-(2- thienyl)-1-(4'-hydroxyphenyl)-2-propen-1-one (V). The order of the cytotoxicity of the compounds was; IV > III > II > I > V. Compound IV, had the highest Hammett and log P values (0.23 and 4.21, respectively) and exerted both highest cytotoxicity and strongest DNA topoisomerase I inhibition. Compounds I and II gave moderate interference with the DNA topoisomerase I while III & V did not interfere with the enzyme.

Benzimidazoles of both natural and synthetic sources are the key components of many bio-active compounds. Several reports have shown antifungal, antiviral, H(2) receptor blocker and antitumor activities for benzimidazoles and their derivatives. In this study, we synthesized twelve bis-benzimidazole derivatives by selecting di(1H-benzo[d]imidazol-2-yl)methane as the main compound. The numbers of carbons at 2 positions of bis-benzimidazole derivatives were changed from 1 to 4, and derivatives were synthesized with methyl substitutions at 5- and/or 6- positions. The compounds were screened via in vitro plasmid superciol relaxation assays using mammalian DNA topoisomerase I and cytostatic assays were carried out against HeLa (cervix adenocarcinoma), MCF7 (breast adenocarcinoma) and A431 (skin epidermoid carcinoma) cells for selected derivatives. Our results suggest that the malonic acid derivatives of bis-benzimidazoles, namely, bis(5-methyl-1H-benzo[d]imidazol-2-yl)methane and bis(5,6-dimethyl-1H-benzo[d]imidazol-2-yl)methane, were remarkably active compounds in interfering with DNA topoisomerase I and the former compound was also found to be cytotoxic against MCF7 and A431 cells. The inhibitory effects obtained with these derivatives are significant as these compounds can be potential sources of anticancer agents.

Benzimidazoles are important compounds because of their antibacterial, antifungal, antimicrobial, antiprotozoal and antihelmintic activities. Some benzimidazole derivatives also interfere with the reactions of DNA topoisomerases, enzymes functioning at almost all stages of the cell cycle. In this study, nine 1H-benzimidazole derivatives with substituents at positions 2 and 5 were synthesized and the structure of the compounds was elucidated by instrumental methods. The characterized compounds were screened to identify if they interfered with mammalian type I DNA topoisomerase activity via in vitro supercoil relaxation assays. Selected compounds were subjected to cytostatic assays using HeLa (cervix adenocarcinoma), MCF7 (breast adenocarcinoma) and A431 (skin epidermoid carcinoma) cells. Our results showed that 5-chloro-2-(2-hydroxyphenyl)-1H-benzimidazole exerted the most profound topoisomerase I inhibition and cytotoxicity.

Cytochrome P450 (CYP) is a heme-containing enzyme superfamily metabolizing a wide variety of xenobiotics, including drugs and carcinogens. The majority of CYP genes are expressed in the liver, however, some CYP isoforms are also reported for a number of extra hepatic tissues. We analyzed Cytochrome P450-2A6, -3A5 and -4B1 mRNAs using real-time reverse-transcriptase polymerase chain reaction (RT-PCR) in a total of 21 homogenized prostate tissues with or without malignancy. We detected a consistent expression of CYP2A6 and CYP3A5 in all, and of CYP4B1 in some (11/21) of the samples at mRNA level. Neither the histopathological status nor the smoking habit of the individuals affected CYP4B1 expression. Our results reflect possible roles for these particular CYPs in therapy and protection of prostate tissue.

Reelin is an extracellular matrix-associated protein important in the regulation of neuronal migration during cerebral cortical development. Point mutations in the RELN gene have been shown to cause an autosomal recessive human brain malformation termed lissencephaly with cerebellar hypoplasia (LCH). Recent work has raised the possibility that reelin may also play a pathogenic role in other neuropsychiatric disorders. We sought, therefore, to define more precisely the phenotype of RELN gene disruption. To do this, we performed a clinical, radiological, and molecular study of a family in whom multiple individuals carry a chromosomal inversion that disrupts the RELN locus. A 6-year-old girl homozygous for the pericentric inversion 46,XX,inv7(p11.2q22) demonstrated the same clinical features that have been previously described in association with RELN point mutations. The girl's brain magnetic resonance imaging (MRI) findings, including pachygyria and severe cerebellar hypoplasia, were identical to those seen with RELN point mutations. Fluorescence in situ hybridization confirmed that one of the breakpoints of this inversion mapped to within the RELN gene, and Western blotting revealed an absence of detectable serum reelin protein. Several relatives who were heterozygous for this inversion were neurologically normal and had no signs of psychotic illness. Our findings demonstrate the distinctive phenotype of LCH, which is easily distinguishable from other forms of lissencephaly. Although RELN appears to be critical for normal cerebral and cerebellar development, its role, if any, in the pathogenesis of psychiatric disorders remains unclear.