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There is a narrative told among healthcare providers that the public stories of trisomy 18 do not reflect the experiences of the many families navigating this diagnosis. This is in the context of a recognised paradigm shift occurring in the treatment of children born with trisomy 18 from one focused solely on comfort to one that considers the potential of medical-surgical interventions to afford survival. This study aims to elicit and explore phenomenologically parents’ narratives of trisomy 18. The focus is on the full spectrum of trisomy 18: whether it was diagnosed before or after birth, whether the child’s life was of short or long duration and whether invasive or palliative care was sought. While trisomy 18 was not univocal of the children’s stories, as a focus of this qualitative inquiry unified them. Healthcare providers may benefit from understanding how trisomy 18 may affect a particular diagnosis experience, whether made during pregnancy or the days after birth when parents are still getting to know their child. As parents live with this diagnosis, pregnancy and the life of their child may be shaped by an uncertainty of a life-limiting condition, whereby care is bounded by what is and is not possible. And, we may appreciate how trisomy 18 imparts meanings on ordinary and extraordinary moments for children and their families in a recognisable form. The understandings gained from this research may support healthcare professionals’ reflective clinical practices as they care for children and their families affected by this diagnosis.

Abstract Background Historically, children born alive with trisomy 18 were considered to have a lethal genetic condition such that no medical interventions were provided. While survival is now recognized to be possible, these children’s lives include aspects of technological dependency, medical complexity, and neurodevelopmental disabilities. Objectives The primary aim of this study was to describe the outcomes of a contemporary Canadian population-based cohort of children born alive with trisomy 18. Methods A retrospective study was conducted to review the records of children born alive with trisomy 18 from January 2012 to December 2023 in Central/Northern Alberta. Demographic and clinical information were abstracted, including features reported in the literature associated with morbidity and mortality. Outcomes were described, including technological dependency, time spent in the hospital, and survival. Results In total, 37 liveborn infants with complete trisomy 18 were identified. While most died in hospital following medical-surgical interventions and/or comfort-care palliation, nine were discharged home. All of these children had been born at term with a birthweight ≥1750 g. While they relied on medical technologies such as home oxygen and feeding tubes at the time of discharge, most were able to spend a considerable amount of time at home rather than being re-hospitalized. At the time of this review, four remain alive varying in age from 6 to 9 years. Conclusions Trisomy 18 is not a homogeneous clinical condition. Some children may have their lives extended to spend their lives at home with their families.

De novo heterozygous variants in CUGBP Elav-like family member 2 ( CELF2 ) have recently been associated with a rare neurodevelopmental disorder, yet the mechanisms linking specific variants to distinct clinical phenotypes remain poorly understood. Here, we reported a cohort of 18 individuals and provided evidence that variants causing CELF2 mislocalization, but not protein-null variants, were associated with seizures. Using proband-derived human cortical neurons and transgenic mouse models, we demonstrated that CELF2 underwent activity-dependent nucleocytoplasmic shuttling in excitatory neurons and that its cytoplasmic retention caused neuronal hyperactivity, elevated seizure susceptibility, and learning and memory deficits. We further found that cytoplasmic CELF2 regulated mRNAs critical for synaptic function and neuronal excitability and implicated in epileptic seizures and intellectual disability. Drug screening further identified AKT signaling as a key regulator of CELF2 nucleocytoplasmic shuttling and a candidate target for reversing neuronal hyperactivity. Together, our findings expand the clinical and genetic spectrum of CELF2-related neurodevelopmental disorders and establish a variant-specific mechanism that links CELF2 mislocalization to neuronal hyperactivity, seizures, and cognitive impairment.

The introduction of next generation sequencing (NGS) technologies has revolutionized the practice of Medical Genetics, and despite initial reticence in its application to prenatal genetics (PG), it is becoming gradually routine, subject to availability. Guidance for the clinical implementation of NGS in PG, in particular whole exome sequencing (ES), has been provided by several professional societies with multiple clinical studies quoting a wide range of testing yields. ES was introduced in our tertiary care center in 2017; however, its use in relation to prenatally assessed cases has been limited to the postnatal period. In this study, we review our approach to prenatal testing including the use of microarray (CMA), and NGS technology (gene panels, ES) over a period of three years. The overall diagnostic yield was 30.4%, with 43.2% of those diagnoses being obtained through CMA, and the majority by using NGS technology (42% through gene panels and 16.6% by ES testing, respectively). Of these, 43.4% of the diagnoses were obtained during ongoing pregnancies. Seventy percent of the abnormal pregnancies tested went undiagnosed. We are providing a contemporary, one tertiary care center retrospective view of a real-life PG practice in the context of an evolving use of NGS within a Canadian public health care system that may apply to many similar jurisdictions around the world.

Background The CTCF insulator protein is a highly conserved zinc finger protein that has been implicated in many aspects of gene regulation and nuclear organization. The protein has been hypothesized to organize the human genome by forming DNA loops. Results In this paper, we report biochemical evidence to support the role for CTCF in forming DNA loops. We have measured DNA bending by CTCF at the chicken HS4 β-globin FII insulator element in vitro and have observed a unique DNA structure with aberrant electrophoretic mobility which we believe to be a DNA loop. CTCF is able to form this unusual DNA structure at two other binding sites: the c-myc P2 promoter and the chicken F1 lysozyme gene silencer. We also demonstrate that the length though not the sequence of the DNA downstream of the binding site is important for the ability of CTCF to form this unusual DNA structure. We hypothesize that a single CTCF protein molecule is able to act as a \"looper\" possibly through the use of several of its zinc fingers. Conclusions CTCF is able to form an unusual DNA structure through the zinc finger domain of the protein. This unusual DNA structure is formed in a directional manner by the CTCF protein. The findings described in this paper suggest mechanisms by which CTCF is able to form DNA loops, organize the mammalian genome and function as an insulator protein.

The overall composition of the mammalian intestinal microbiota varies between individuals: within each individual there are differences along the length of the intestinal tract related to host nutrition, intestinal motility and secretions. Mucus is a highly regenerative protective lubricant glycoprotein sheet secreted by host intestinal goblet cells; the inner mucus layer is nearly sterile. Here we show that the outer mucus of the large intestine forms a unique microbial niche with distinct communities, including bacteria without specialized mucolytic capability. Bacterial species present in the mucus show differential proliferation and resource utilization compared with the same species in the intestinal lumen, with high recovery of bioavailable iron and consumption of epithelial-derived carbon sources according to their genome-encoded metabolic repertoire. Functional competition for existence in this intimate layer is likely to be a major determinant of microbiota composition and microbial molecular exchange with the host. The inner layer of the mucus that covers our intestine is nearly sterile. Here, the authors show in mice that the outer mucus layer constitutes a unique microbial niche hosting bacterial communities with distinct proliferation rates and resource utilization activities.

The lower intestine of adult mammals is densely colonized with nonpathogenic (commensal) microbes. Gut bacteria induce protective immune responses, which ensure host-microbial mutualism. The continuous presence of commensal intestinal bacteria has made it difficult to study mucosal immune dynamics. Here, we report a reversible germ-free colonization system in mice that is independent of diet or antibiotic manipulation. A slow (more than 14 days) onset of a long-lived (half-life over 16 weeks), highly specific anticommensal immunoglobulin A (IgA) response in germ-free mice was observed. Ongoing commensal exposure in colonized mice rapidly abrogated this response. Sequential doses lacked a classical prime-boost effect seen in systemic vaccination, but specific IgA induction occurred as a stepwise response to current bacterial exposure, such that the antibody repertoire matched the existing commensal content.

Colonization by the microbiota causes a marked stimulation of B cells and induction of immunoglobulin, but mammals colonized with many taxa have highly complex and individualized immunoglobulin repertoires 1 , 2 . Here we use a simplified model of defined transient exposures to different microbial taxa in germ-free mice 3 to deconstruct how the microbiota shapes the B cell pool and its functional responsiveness. We followed the development of the immunoglobulin repertoire in B cell populations, as well as single cells by deep sequencing. Microbial exposures at the intestinal mucosa generated oligoclonal responses that differed from those of germ-free mice, and from the diverse repertoire that was generated after intravenous systemic exposure to microbiota. The IgA repertoire—predominantly to cell-surface antigens—did not expand after dose escalation, whereas increased systemic exposure broadened the IgG repertoire to both microbial cytoplasmic and cell-surface antigens. These microbial exposures induced characteristic immunoglobulin heavy-chain repertoires in B cells, mainly at memory and plasma cell stages. Whereas sequential systemic exposure to different microbial taxa diversified the IgG repertoire and facilitated alternative specific responses, sequential mucosal exposure produced limited overlapping repertoires and the attrition of initial IgA binding specificities. This shows a contrast between a flexible response to systemic exposure with the need to avoid fatal sepsis, and a restricted response to mucosal exposure that reflects the generic nature of host–microbial mutualism in the mucosa. A mouse model of systemic versus mucosal exposure to microbial taxa reveals that the former provokes a flexible B cell response with a diverse immunoglobulin repertoire, whereas the latter generates a more-restricted response.

Commensal bacteria in the lower intestine of mammals are 10 times as numerous as the body's cells. We investigated the relative importance of different immune mechanisms in limiting the spread of the intestinal microbiota. Here, we reveal a flexible continuum between innate and adaptive immune function in containing commensal microbes. Mice deficient in critical innate immune functions such as Toll-like receptor signaling or oxidative burst production spontaneously produce high-titer serum antibodies against their commensal microbiota. These antibody responses are functionally essential to maintain host-commensal mutualism in vivo in the face of innate immune deficiency. Spontaneous hyper-activation of adaptive immunity against the intestinal microbiota, secondary to innate immune deficiency, may clarify the underlying mechanisms of inflammatory diseases where immune dysfunction is implicated.

B cell activation factor of the TNF family (BAFF) is a potent B cell survival factor. BAFF overexpressing transgenic mice (BAFF-Tg mice) exhibit features of autoimmune disease, including B cell hyperplasia and hypergammaglobulinemia, and develop fatal nephritis with age. However, basal serum IgA levels are also elevated, suggesting that the pathology in these mice may be more complex than initially appreciated. Consistent with this, we demonstrate here that BAFF-Tg mice have mesangial deposits of IgA along with high circulating levels of polymeric IgA that is aberrantly glycosylated. Renal disease in BAFF-Tg mice was associated with IgA, because serum IgA was highly elevated in nephritic mice and BAFF-Tg mice with genetic deletion of IgA exhibited less renal pathology. The presence of commensal flora was essential for the elevated serum IgA phenotype, and, unexpectedly, commensal bacteria-reactive IgA antibodies were found in the blood. These data illustrate how excess B cell survival signaling perturbs the normal balance with the microbiota, leading to a breach in the normal mucosal-peripheral compartmentalization. Such breaches may predispose the nonmucosal system to certain immune diseases. Indeed, we found that a subset of patients with IgA nephropathy had elevated serum levels of a proliferation inducing ligand (APRIL), a cytokine related to BAFF. These parallels between BAFF-Tg mice and human IgA nephropathy may provide a new framework to explore connections between mucosal environments and renal pathology.