Chromatin targeting of the RNF12/RLIM E3 ubiquitin ligase controls transcriptional responses.

Protein ubiquitylation regulates key biological processes including transcription. This is exemplified by the E3 ubiquitin ligase RNF12/RLIM, which controls developmental gene expression by ubiquitylating the REX1 transcription factor and is mutated in an X-linked intellectual disability disorder. However, the precise mechanisms by which ubiquitylation drives specific transcriptional responses are not known. Here, we show that RNF12 is recruited to specific genomic locations via a consensus sequence motif, which enables co-localisation with REX1 substrate at gene promoters. Surprisingly, RNF12 chromatin recruitment is achieved via a non-catalytic basic region and comprises a previously unappreciated N-terminal autoinhibitory mechanism. Furthermore, RNF12 chromatin targeting is critical for REX1 ubiquitylation and downstream RNF12-dependent gene regulation. Our results demonstrate a key role for chromatin in regulation of the RNF12-REX1 axis and provide insight into mechanisms by which protein ubiquitylation enables programming of gene expression.

Efficient generation of ETX embryoids that recapitulate the entire window of murine egg cylinder development.

The murine embryonic-trophoblast-extra-embryonic endoderm (ETX) model is an integrated stem cell-based model to study early postimplantation development. It is based on the self-assembly potential of embryonic, trophoblast, and hypoblast/primitive/visceral endoderm-type stem cell lines (ESC, TSC, and XEN, respectively) to arrange into postimplantation egg cylinder-like embryoids. Here, we provide an optimized method for reliable and efficient generation of ETX embryoids that develop into late gastrulation in static culture conditions. It is based on transgenic Gata6-overproducing ESCs and modified assembly and culture conditions. Using this method, up to 43% of assembled ETX embryoids exhibited a correct spatial distribution of the three stem cell derivatives at day 4 of culture. Of those, 40% progressed into ETX embryoids that both transcriptionally and morphologically faithfully mimicked in vivo postimplantation mouse development between E5.5 and E7.5. The ETX model system offers the opportunity to study the murine postimplantation egg cylinder stages and could serve as a source of various cell lineage precursors.

Synthesis and investigation of the trypanocidal potential of novel 1,2,3-triazole-selenide hybrids.

Chagas Disease is caused by the protozoan Trypanosoma cruzi and is considered a tropical neglected disease by the World Health Organization (WHO). The main drugs used in the therapy of the disease are obsolete and, as a result, it still kills millions of people every year. Therefore, the development of new drugs is urgent, as is the research reported in this article, in which new triazole selenides were synthesized through a simple methodology and to evaluate their potential against T. cruzi, through a combination of in vitro and in silico assays. With the combination of two molecular scaffolds already known for this activity, sixteen new hybrid compounds were obtained, showing yields ranging from 40 to 90%, and their biological potentials were tested. Two of the evaluated hybrids showed potent trypanocidal activity (11m and 11n), comparable to the positive control benznidazole. Density functional theory (DFT) studies were correlated with cyclic voltammetry assays to investigate the LUMO energy, which demonstrated a correlation with the observed trypanocidal activity. These results are promising, considering 11m and 11n as hit compounds in the development of new antichagasic drugs.

SPEN is required for Xist upregulation during initiation of X chromosome inactivation.

At initiation of X chromosome inactivation (XCI), Xist is monoallelically upregulated from the future inactive X (Xi) chromosome, overcoming repression by its antisense transcript Tsix. Xist recruits various chromatin remodelers, amongst them SPEN, which are involved in silencing of X-linked genes in cis and establishment of the Xi. Here, we show that SPEN plays an important role in initiation of XCI. Spen null female mouse embryonic stem cells (ESCs) are defective in Xist upregulation upon differentiation. We find that Xist-mediated SPEN recruitment to the Xi chromosome happens very early in XCI, and that SPEN-mediated silencing of the Tsix promoter is required for Xist upregulation. Accordingly, failed Xist upregulation in Spen-/- ESCs can be rescued by concomitant removal of Tsix. These findings indicate that SPEN is not only required for the establishment of the Xi, but is also crucial in initiation of the XCI process.

Psychological Treatment for Patients Receiving Radiation: Results of NRG Oncology/RTOG 0841.

PURPOSE: NRG/RTOG 0841 assessed the feasibility of a depression screening procedure in patients receiving radiation therapy (RT). As a secondary endpoint, availability and barriers to psychosocial care data were collected in hopes of providing recommendations for improved psychosocial care among patients receiving RT. METHODS AND MATERIALS: Patients starting RT were prospectively recruited and assessed with self-reported distress screening tools. Patients exceeding a validated cutoff and a sample of patients who screened negative received the Structured Clinical Interview for DSM-IV (SCID) mood disorder modules via telephone. During that SCID evaluation, patients completed a validated scale ranking interview on barriers to psychosocial care and interest in various psychosocial intervention modalities. RESULTS: A total of 463 patients from 35 community-based and 2 academic RT oncology sites were recruited. Of the 455 eligible, 75 (16%) exceeded screening cutoffs for depressive symptoms. From this group, 78 patients completed the SCID; most were female (76%), white (88%), and had breast cancer (55%). Overall, the most common barriers to treatment, regardless of insurance, were costs (58%), daily responsibilities (44%), and physical health symptoms (38%). Patients from RT facilities without mental health services were significantly more likely to report difficulty with physical health problems, specifically serious illness and walking, compared with those treated at RT facilities with services (P = .013 and P = .039, respectively). Overall, there was interest in obtaining psychosocial services with face-to-face counseling at the cancer center and printed educational materials as the most commonly preferred interventions. Patients with difficult barriers to psychosocial interventions were significantly less interested in support away from the cancer center (P = .016), telephone and Internet counseling (P = .0062 &P = .011), and Internet support (P = .0048). CONCLUSION: Radiation oncology patients are interested in obtaining psychosocial services but face barriers to access to mental health services including cost, debilitating symptoms, and time constraints that prevent adequate care.

Transcriptome analysis of the zebrafish atoh7-/- Mutant, lakritz, highlights Atoh7-dependent genetic networks with potential implications for human eye diseases.

Expression of the bHLH transcription protein Atoh7 is a crucial factor conferring competence to retinal progenitor cells for the development of retinal ganglion cells. Several studies have emerged establishing ATOH7 as a retinal disease gene. Remarkably, such studies uncovered ATOH7 variants associated with global eye defects including optic nerve hypoplasia, microphthalmia, retinal vascular disorders, and glaucoma. The complex genetic networks and cellular decisions arising downstream of atoh7 expression, and how their dysregulation cause development of such disease traits remains unknown. To begin to understand such Atoh7-dependent events in vivo, we performed transcriptome analysis of wild-type and atoh7 mutant (lakritz) zebrafish embryos at the onset of retinal ganglion cell differentiation. We investigated in silico interplays of atoh7 and other disease-related genes and pathways. By network reconstruction analysis of differentially expressed genes, we identified gene clusters enriched in retinal development, cell cycle, chromatin remodeling, stress response, and Wnt pathways. By weighted gene coexpression network, we identified coexpression modules affected by the mutation and enriched in retina development genes tightly connected to atoh7. We established the groundwork whereby Atoh7-linked cellular and molecular processes can be investigated in the dynamic multi-tissue environment of the developing normal and diseased vertebrate eye.

Loss of function mutations in essential genes cause embryonic lethality in pigs.

Lethal recessive alleles cause pre- or postnatal death in homozygous affected individuals, reducing fertility. Especially in small size domestic and wild populations, those alleles might be exposed by inbreeding, caused by matings between related parents that inherited the same recessive lethal allele from a common ancestor. In this study we report five relatively common (up to 13.4% carrier frequency) recessive lethal haplotypes in two commercial pig populations. The lethal haplotypes have a large effect on carrier-by-carrier matings, decreasing litter sizes by 15.1 to 21.6%. The causal mutations are of different type including two splice-site variants (affecting POLR1B and TADA2A genes), one frameshift (URB1), and one missense (PNKP) variant, resulting in a complete loss-of-function of these essential genes. The recessive lethal alleles affect up to 2.9% of the litters within a single population and are responsible for the death of 0.52% of the total population of embryos. Moreover, we provide compelling evidence that the identified embryonic lethal alleles contribute to the observed heterosis effect for fertility (i.e. larger litters in crossbred offspring). Together, this work marks specific recessive lethal variation describing its functional consequences at the molecular, phenotypic, and population level, providing a unique model to better understand fertility and heterosis in livestock.

Screening for depression in cancer patients receiving radiotherapy: Feasibility and identification of effective tools in the NRG Oncology RTOG 0841 trial.

BACKGROUND: Brief tools are needed to screen oncology outpatients for depressive symptoms. METHODS: Patients starting radiotherapy for the first diagnosis of any tumor completed distress screening tools, including the 9-item Patient Health Questionnaire (PHQ-9), the 2-item Patient Health Questionnaire (PHQ-2), the National Comprehensive Cancer Network Distress Thermometer (NCCN-DT), and the Hopkins Symptom Checklist (HSCL) (25-item version). Patients exceeding validated cutoff scores and a systematic sample of patients whose screening was negative completed the Structured Clinical Interview for DSM-IV (SCID) mood disorder modules via telephone. RESULTS: Four hundred sixty-three patients from 35 community-based radiation oncology sites and 2 academic radiation oncology sites were recruited. Sixty-six percent of the 455 eligible patients (n = 299) were women, and the eligible patients had breast (45%), gastrointestinal (11%), lung (10%), gynecologic (6%), or other cancers (27%). Seventy-five (16.5%) exceeded screening cutoffs for depressive symptoms. Forty-two of these patients completed the SCID. Another 37 patients whose screening was negative completed the SCID. Among the 79 patients completing the SCID, 8 (10.1%) met the criteria for major depression, 2 (2.5%) met the criteria for dysthymia, and 6 (7.6%) met the criteria for an adjustment disorder. The PHQ-2 demonstrated good psychometric properties for screening for mood disorders with a cutoff score of ≥3 (receiver operating characteristic area under the curve [AUC], 0.83) and was comparable to the PHQ-9 ( > 9; AUC = 0.85). The NCCN-DT did not detect depression (AUC = 0.59). CONCLUSIONS: The PHQ-2 demonstrated good psychometric properties for screening for mood disorders, which were equivalent to the PHQ-9 and superior to the NCCN-DT. These findings support using the PHQ-2 to identify patients in need of further assessment for depression, which has a low prevalence but is a clinically significant comorbidity. These findings could inform the implementation of distress screening accreditation standards. Cancer 2017;123:485-493. © 2016 American Cancer Society.

The Inhibitory Receptor NKG2A Sustains Virus-Specific CD8⁺ T Cells in Response to a Lethal Poxvirus Infection.

CD8(+) T cells and NK cells protect from viral infections by killing virally infected cells and secreting interferon-γ. Several inhibitory receptors limit the magnitude and duration of these anti-viral responses. NKG2A, which is encoded by Klrc1, is a lectin-like inhibitory receptor that is expressed as a heterodimer with CD94 on NK cells and activated CD8(+) T cells. Previous studies on the impact of CD94/NKG2A heterodimers on anti-viral responses have yielded contrasting results and the in vivo function of NKG2A remains unclear. Here, we generated Klrc1(-/-) mice and found that NKG2A is selectively required for resistance to ectromelia virus (ECTV). NKG2A functions intrinsically within ECTV-specific CD8(+) T cells to limit excessive activation, prevent apoptosis, and preserve the specific CD8(+) T cell response. Thus, although inhibitory receptors often cause T cell exhaustion and viral spreading during chronic viral infections, NKG2A optimizes CD8(+) T cell responses during an acute poxvirus infection.

Comparison of lifestyle and practice patterns between male and female Canadian ophthalmologists.

OBJECTIVE: To identify sex differences in lifestyle and practice patterns of Canadian ophthalmologists. DESIGN: Web-based national survey. PARTICIPANTS: Members of the Canadian Ophthalmological Society. METHODS: A 48-item questionnaire was sent electronically. Analysis of results was completed using χ(2) and Fisher's exact tests where appropriate. RESULTS: Of 385 respondents (30%), 102 were female and 283 male. Several statistically significant differences exist in lifestyle and practice patterns. Fifty-one percent of females operate less than 2 days per month as compared with 36% of males (p = 0.01) despite similar clinical hours. No statistically significant differences were found in other practice pattern parameters including laser refractive surgery, hospital affiliation, university appointment/rank, and number of peer-review publications. Ninety percent of males and 81% of females report having ≥1 children, but males report greater number of children (p < 0.001). Females are commonly the primary caregiver, whereas males report their partner as primary caregiver (p < 0.001). Fifty-two percent of females are unhappy with the amount of parental leave (p < 0.001). Fifty-one percent of females believe that childbearing slowed or markedly slowed career progress, as compared with 15% of males (p < 0.001). Both female (83%) and male (87%) ophthalmologists report high career satisfaction (p = 0.43). CONCLUSIONS: Differences in practice patterns between males and females in our analysis surround surgical time, with no difference seen in other practice patterns or academic achievements. Differences in family patterns surround household and childrearing duties. Despite differences, both males and females report high satisfaction across several professional and personal parameters. Compared with previous studies, this suggests a change in practice patterns over time.

Isolation of murine natural killer cells.

This unit describes the isolation of natural killer (NK) cells from mouse spleen. The basic protocol describes a method for preparing a highly purified NK cell population from mouse spleen by depletion of contaminating cells with selected monoclonal antibodies (MAbs) and magnetic separation. There are several advantages to this negative selection process. One of these is that the NK cells are not coated with antibody and, therefore, are not at risk of functional perturbation by antibody cross-linking. Additionally, negative selection provides a way to isolate diverse subpopulations of NK cells without selectively purifying a specific subpopulation. Following enrichment, NK cell purity can be assessed by cell surface phenotype using flow cytometry.

[Benefit of skull vibration-induced nystagmus test in occupational medicine]. / Intérêt du test de vibration osseux vestibulaire en médecine du travail.

BACKGROUND: Nystagmus induced by vibrations (NIV), has been optimized by the present authors this last decade. The skull vibration-induced nystagmus test (SVINT) can be designated as a high-frequency global "vestibular Weber test" and can be considered as an office-based examination to detect vestibular asymmetry. The aim of this study is to define the tolerance of the SVINT as well as its comparison to the simplified caloric test of Veits (CTV) in normal workers during the pre-employment visit at the occupational medicine center. MATERIAL AND METHODS: The vestibular function has been evaluated by the SVINT and the CTV in 87 healthy workers. The tolerance of the two procedures has been evaluated by a 4-items questionnaire (nausea, vomiting, sweating, asthenia). RESULTS: The caloric test was normal in each worker. The SVINT was positive in one patient who had a partial unilateral vestibular dysfunction related to trauma. The mean duration of the procedure was 15 min for CTV and 1 min for SVINT. Side effects (nausea, vomiting, sweating, asthenia) were present in 50% of the workers following CTV and in only one patient after SVINT. The SVINT demonstrated significantly less side effects for each item (p < 0.0001). CONCLUSIONS: SVINT is a valid, rapid, low-cost clinical screening test and does not cause patient discomfort. It is suggested that this test which explores vestibular high frequencies and is not modified by vestibular compensation is useful for the diagnostic screening of workers' vestibular dysfunction, when combined with other vestibular tests and complements the CTV.

Occupational risk factors for sinonasal inverted papilloma: a case-control study.

OBJECTIVES: Sinonasal inverted papilloma (IP) is an uncommon benign tumour characterised by frequent recurrence and, in approximately 10% of cases, by neoplastic transformation. IP aetiology is unknown but human papillomavirus is detectable in about one quarter of tumours. As some occupational hazards have been reported to be possible risk factors for IP, the aim of this study was to assess risk for sinonasal IP associated with prior exposure to suspected occupational risk factors for sinonasal malignancies. METHODS: Between 1996 and 2007, data on incident cases were collected from hospitals throughout the Piedmont region of Italy by the regional sinonasal cancer registry. A questionnaire on occupational history, completed by 127 cases and 337 hospital controls, was used to assign previous exposure to a list of 17 occupational hazards. The relationship between IP and cumulative exposure to these hazards was explored using unconditional logistic regression to statistically adjust for age, sex, area of residence, smoking and co-exposures. RESULTS: The risk of IP was significantly increased for ever exposure to welding fumes (OR 2.14) and organic solvents (OR 2.11) after controlling for potential confounders. For organic solvents only, a significant association with continuous cumulative exposure and a significant trend in risk across ordered cumulative exposure categories was found. CONCLUSIONS: The present study revealed a significant association and a significant dose-response relationship between occupational exposure to organic solvents and IP. The lack of a dose-response relationship for welding fumes suggests that the observed association with ever exposure should be interpreted with caution.

[Proposal of entering the mastoid vibration test in health surveillance of workers exposed to industrial solvents]. / Proposta di inserimento del test vibratorio mastoideo nella sorveglianza sanitaria di lavoratori esposti a solventi organici industriali.

In view of the use of solvents and consequently the number of exposed subjects, health surveillance should include instrumental exams to highlight at an early stage alterations of health resulting from exposure. We evaluated 40 workers with chronic exposure to low-level xylene, toluene, fluorene and anthracene, showing that vestibular system was altered in a fair percentage of cases, compared to a control group characterized by 40 workers of the same age not exposed to solvents. The two groups were simultaneously exposed to noise. It is concluded that occupational exposure to industrial organic solvents may lead to chronic alteration of the vestibular system with possible alterations also on work capacity even below the established limits. Second, an assessment of the vestibular system should be introduced in the health surveillance of workers exposed, in which, in our opinion, the mastoid vibration test is a diagnostic tool absolutely valid and simple to perform.

Inhibition of influenza virus replication via small molecules that induce the formation of higher-order nucleoprotein oligomers.

Influenza nucleoprotein (NP) plays multiple roles in the virus life cycle, including an essential function in viral replication as an integral component of the ribonucleoprotein complex, associating with viral RNA and polymerase within the viral core. The multifunctional nature of NP makes it an attractive target for antiviral intervention, and inhibitors targeting this protein have recently been reported. In a parallel effort, we discovered a structurally similar series of influenza replication inhibitors and show that they interfere with NP-dependent processes via formation of higher-order NP oligomers. Support for this unique mechanism is provided by site-directed mutagenesis studies, biophysical characterization of the oligomeric ligand:NP complex, and an X-ray cocrystal structure of an NP dimer of trimers (or hexamer) comprising three NP_A:NP_B dimeric subunits. Each NP_A:NP_B dimeric subunit contains two ligands that bridge two composite, protein-spanning binding sites in an antiparallel orientation to form a stable quaternary complex. Optimization of the initial screening hit produced an analog that protects mice from influenza-induced weight loss and mortality by reducing viral titers to undetectable levels throughout the course of treatment.

A case-control study on occupational risk factors for sino-nasal cancer.

OBJECTIVES: Sino-nasal cancer has been consistently associated with exposure to wood dust, leather dust, nickel and chromium compounds; for other occupational hazards, the findings are somewhat mixed. The aim of this study was to investigate the risk of sino-nasal epithelial cancer (SNEC) by histological type with prior exposure to suspected occupational risk factors and, in particular, those in metalworking. METHODS: Between 1996 and 2000, incident cases were collected on a monthly basis from hospitals throughout the Piedmont region of Italy by the regional Sino-nasal Cancer Registry. A questionnaire on occupational history, completed by 113 cases and 336 hospital controls, was used to assign exposure to occupational hazards. The relationship between SNEC and cumulative exposure to these hazards was explored using unconditional logistic regression to statistically adjust for age, sex, smoking and co-exposures, allowing for a 10-year latency period. RESULTS: The risk of adenocarcinoma was significantly increased with ever-exposure to wood dust (odds ratio; OR = 58.6), and to leather dust (OR = 32.8) and organic solvents (OR = 4.3) after controlling for wood dust, whereas ever-exposure to welding fumes (OR = 3.7) and arsenic (OR = 4.4) significantly increased the risk for squamous cell carcinoma. For each of these hazards, a significant increasing trend in risk across ordered cumulative exposure categories was found and, except for arsenic, a significantly increased risk with ever-exposure at low intensity. Treating cumulative exposure on a continuous scale, a significant effect of textile dusts was also observed for adenocarcinoma. For a mixed group of other histological types, a significant association was found with wood dust and organic solvents. CONCLUSIONS: Some occupational risk factors for SNEC were confirmed, and dose-response relationships were observed for other hazards that merit further investigation. The high risk for adenocarcinoma with low-intensity exposure to wood dust lends support for a reduction in the occupational threshold value.

Ly49h is necessary for genetic resistance to murine cytomegalovirus.

Natural killer (NK) cells play critical roles in antiviral immunity. While the importance of effector mechanisms such as interferons has been demonstrated through knockout mice, specific mechanisms of how viruses are recognized and controlled by NK cells are less well defined. Previous genetic studies have mapped the resistance genes for murine cytomegalovirus (MCMV), herpes simplex virus-1 (HSV-1), and ectromelia virus to the NK gene complex on murine chromosome 6, a region containing the polymorphic Ly49 and Nkrp1 families. Genetic resistance to MCMV in C57BL/6 has been attributed to Ly49H, an activation receptor, through susceptibility of the recombinant inbred strain BXD-8 that lacks Ly49h (also known as Klra8) but derived about half of its genome from its DBA/2 progenitor. However, it remained possible that epigenetic effects could account for the MCMV phenotype in BXD-8 mice. Herein, we report the generation of a novel congenic murine strain, B6.BXD8-Klra8 ( Cmv1-del )/Wum, on the C57BL/6 genetic background to evaluate the effect of deletion of a single NK activation receptor, Ly49H. Deletion of Ly49H rendered mice much more susceptible to MCMV infection. This increase in susceptibility did not appear to be a result of a difference in NK cell expansion or interferon-gamma (IFN-gamma) production between the C57BL/6 and the B6.BXD8 strains. On the other hand, the deletion of Ly49h did not otherwise affect NK cell maturation or Ly49D expression and had no effect on susceptibility to HSV-1 or ectromelia virus. In conclusion, Ly49h is necessary for genetic resistance to MCMV, but not HSV-1 or ectromelia virus.

Vagal paragangliomas: two case reports.

Two uncommon cases of paragangliomas arising from the vagus nerve are described. The first patient underwent surgery for suspected carotid body tumour. In the second patient, computed tomography scan and digital angiography allowed a correct pre-operative diagnosis to be made. These cases confirm the prevalence of vagal paragangliomas in female sex and middle age, and the possibility of multiple similar tumours in the same patient. Histological benign features, absence of neurological symptoms, of local invasion or intracranial extension confirm the frequent benign behaviour of these neoplasms. Lack of catecholamine secretion confirms the low incidence of functioning tumours. Contrast computed tomography and digital angiography still remain the gold standard reliable instruments for diagnosis despite the success of magnetic resonance imaging, magnetic resonance angiography and octreotide scintigraphy to detect head and neck paragangliomas. A transcervical approach, without mandibulotomy, is suitable too for large tumours but complete removal, with sparing of involved segments of the vagus nerve, is rarely possible. Post-operative neurological morbidity is still an unsolved issue and, therefore, rehabilitation of deglutition and phonation is an integral part of management.

The gene for paroxysmal non-kinesigenic dyskinesia encodes an enzyme in a stress response pathway.

Paroxysmal non-kinesigenic dyskinesia (PNKD) is characterized by spontaneous hyperkinetic attacks that are precipitated by alcohol, coffee, stress and fatigue. We report mutations in the myofibrillogenesis regulator 1 (MR-1) gene causing PNKD in 50 individuals from eight families. The mutations cause changes (Ala to Val) in the N-terminal region of two MR-1 isoforms. The MR-1L isoform is specifically expressed in brain and is localized to the cell membrane while the MR-1S isoform is ubiquitously expressed and shows diffuse cytoplasmic and nuclear localization. Bioinformatic analysis reveals that the MR-1 gene is homologous to the hydroxyacylglutathione hydrolase (HAGH) gene. HAGH functions in a pathway to detoxify methylglyoxal, a compound present in coffee and alcoholic beverages and produced as a by-product of oxidative stress. Our results suggest a mechanism whereby alcohol, coffee and stress may act as precipitants of attacks in PNKD. Stress response pathways will be important areas for elucidation of episodic disease genetics where stress is a common precipitant of many common disorders like epilepsy, migraine and cardiac arrhythmias.

Genetically linked C-type lectin-related ligands for the NKRP1 family of natural killer cell receptors.

The natural killer (NK) gene complex (NKC) encodes orphan lectin-like NK cell receptors that may explain uncharacterized NK cell specificities. Unlike other NKC-encoded receptors that recognize molecules with major histocompatibility complex (MHC) class I folds, here we show that mouse Nkrp1d and Nkrp1f bind specific C-type lectin-related (Clr) molecules. Nkrp1d mediated inhibition when recognizing Clrb, a molecule expressed in dendritic cells and macrophages. Nkrp1 (official gene name, Klrb1) and Clr are intertwined in a genetically conserved NKC region showing recombination suppression, reminiscent of plant self-incompatibility loci. Thus, these findings broaden the 'missing-self' hypothesis from solely involving MHC class I to including related NK cell receptors for lectin-like ligands, and reflect genetic strategies for biological self-recognition processes in other species.