Sibling Pairs Research Articles

Association of Acute Respiratory Failure in Early Childhood With Long-term Neurocognitive Outcomes

Approximately 23 700 US children undergo invasive mechanical ventilation for acute respiratory failure annually, with unknown long-term effects on neurocognitive function. To evaluate neurocognitive outcomes of children who survive pediatric intensive care unit (PICU) hospitalization for acute respiratory failure compared with their biological siblings. Prospective sibling-matched cohort study conducted at 31 US PICUs and associated neuropsychology testing centers. Patients were 8 years or younger with a Pediatric Cerebral Performance Category score of 1 (normal) before PICU admission and less than or equal to 3 (no worse than moderate neurocognitive dysfunction) at PICU discharge, excluding patients with a history of neurocognitive deficits or who were readmitted and underwent mechanical ventilation. Biological siblings were aged 4 to 16 years at testing, with Pediatric Cerebral Performance Category score of 1 and no history of mechanical ventilation or general anesthesia. A total of 121 sibling pairs were enrolled from September 2, 2014, to December 13, 2017, and underwent neurocognitive testing starting March 14, 2015. The date of the final follow-up was November 6, 2018. Critical illness and PICU treatment for acute respiratory failure. The primary outcome was IQ, estimated by the age-appropriate Vocabulary and Block Design subtests of the Wechsler Intelligence Scale. Secondary outcomes included measures of attention, processing speed, learning and memory, visuospatial skills, motor skills, language, and executive function. Evaluations occurred 3 to 8 years after hospital discharge. Patients (n = 121; 55 [45%] female patients) underwent PICU care at a median (IQR) age of 1.0 (0.2-3.2) years, received a median (IQR) of 5.5 (3.1-7.7) days of invasive mechanical ventilation, and were tested at a median (IQR) age of 6.6 (5.4-9.1) years. Matched siblings (n = 121; 72 [60%] female siblings) were tested at a median (IQR) age of 8.4 (7.0-10.2) years. Patients had a lower mean estimated IQ than matched siblings (101.5 vs 104.3; mean difference, -2.8 [95% CI, -5.4 to -0.2]). Among secondary outcomes, patients had significantly lower scores than matched siblings on nonverbal memory (mean difference, -0.9 [95% CI, -1.6 to -0.3]), visuospatial skills (mean difference, -0.9 [95% CI, -1.8 to -0.1]), and fine motor control (mean difference, -3.1 [95% CI, -4.9 to -1.4]) and significantly higher scores on processing speed (mean difference, 4.4 [95% CI, 0.2-8.5]). There were no significant differences in the remaining secondary outcomes, including attention, verbal memory, expressive language, and executive function. Among children, survival of PICU hospitalization for respiratory failure and discharge without severe cognitive dysfunction was associated with significantly lower subsequent IQ scores compared with matched siblings. However, the magnitude of the difference was small and of uncertain clinical importance.

You can go your own way: No evidence for social behavior based on kinship or familiarity in captive juvenile box turtles

Behavioral interactions between conspecific animals can be influenced by relatedness and familiarity. Compared to other vertebrate taxa, considering such aspects of social behavior when housing captive reptiles has received less attention, despite the implications this could have for informing husbandry practices, enhancing welfare, and influencing outcomes of conservation translocations. To test how kinship and familiarity influenced social behavior in juvenile Eastern Box Turtles (Terrapene carolina), we reared 16 captive-born individuals under semi-natural conditions in four equally sized groups, where each group comprised pairs of siblings and non-siblings. Using separation distance between pairs of turtles in rearing enclosures as a measure of gregariousness, we found no evidence suggesting siblings more frequently interacted with one another compared to non-relatives over the first five months of life (β = −0.016, 95% CI: −0.117 to 0.084). Average pair separation distance decreased during this time (β = −0.146, 95% CI: −0.228 to −0.063) but may have been due to turtles aggregating around concentrated resources like heat and moist retreat areas as cold winter temperatures approached. When subjects were eight months old, we measured repeated separation distances between unique pair combinations in an experimental environment and similarly found no support for gregariousness (associations) being influenced by kinship or familiarity (β = −1.554, 95% CI: −9.956 to 6.848). Additionally, neither differences in body size between pairs of turtles (β = −22.289, 95% CI: −68.448 to 23.870) nor the five-minute time interval during the 90-minute trial (P ≥ 0.18) had any apparent effect on associations. Agonistic interactions between individuals were never observed. Encouragingly, based on our results, group housing and rearing of juvenile box turtles did not appear to negatively impact their welfare. Unlike findings for other taxa, including some reptiles, our results suggest strategically housing groups of juvenile T. carolina to maintain social stability may not be an important husbandry consideration or necessary when planning releases of captive-reared individuals for conservation purposes.

Neurocognitive profile of adolescents with early-onset schizophrenia and their unaffected siblings

Background We investigated the neurocognitive profiles of Early-Onset Schizophrenia (EOS; onset before age 18) and paired unaffected siblings and the little-studied effect of age-of-onset and duration of illness on cognitive performance. Methods 31 EOS probands, and 31 of their siblings, had four cognitive domains assessed: (a) Memory: California Verbal Learning Test, and the Wechsler Memory Scale-Revised; (b) Working memory: Digit Span; (c) Attention: Degraded-Stimulus Continuous Performance Test, Span of Apprehension (SPAN), and Trail Making Test (TMT) part A; (d) Executive function: Wisconsin card sorting task, and TMT part B. Diagnosis was confirmed using the structured clinical interview for DSM-IV. Results While EOS showed a generalised neurocognitive deficit (0.25–0.50 effect size) compared with siblings, across all cognitive domains, significantly greater patient deficits were observed with, working memory, attention, and executive function and minimal differences for digit span forward, block design and false alarms on the SPAN-12 confirmed by repeated measures MANOVA. Patients with earlier onset (12–15) showed greater deficits on false alarm and digits backward scores. Siblings showed individual cognitive task profiles similar to patients, confirming familial effects. EOS showed much more variable scores than siblings with more individual tasks showing 2 SD deficits than siblings. Long duration patients had greater z-score variability across tasks. Conclusions Duration of illness was a more important characteristic in patients with onset 16 and over than in younger onset patients with comparable durations. Both the similarity of sibling pair profiles and greater patient variability across task provide further support for neurobiological heterogeneity in schizophrenia.

Microsatellite markers as a tool for active germplasm management and bridging the gap between national and local collections of apple

Simple sequence repeat (SSR) microsatellite markers have been extensively used to identify duplication and analyse genetic diversity in germplasm collections of apple. Here, we present findings from the use of a standard set of SSR loci in the managed repropagation of a significant international germplasm collection: the UK National Fruit Collection (NFC). A subset of eight SSR loci was deemed sufficient to distinguish all apart from the clonal relatives across a sample of 1995 accessions, with a single exception being one pair of full siblings. In total, 99% of accessions were able to be confirmed present and correct after the replacement of trees initially identified to be incorrectly propagated. In parallel to the curation of the collection itself, through an initiative led by the UK local apple enthusiast community, 3373 SSR profiles for apples held in local collections were compared to the NFC holdings. Overall, in both sets of material, diversity remained high with average gene diversity values of 0.800 and 0.812 in the NFC holdings and local collections, respectively. Accessions in local collections were not found to differ in their overall coverage of genetic diversity to that of the NFC collection (FST = 0.0035) although significant numbers of locally valued, and genetically distinguishable individuals were identified, some of which may represent ‘lost’ cultivars.

Novel CD55 Mutation Associated With Severe Small Bowel Ulceration Mimicking Inflammatory Bowel Disease in a Pair of Siblings.

Novel CD55 Mutation Associated With Severe Small Bowel Ulceration Mimicking Inflammatory Bowel Disease in a Pair of Siblings.

Brothers and sisters sharing in the care of a parent with dementia.

Brothers’ and sisters’ experiences providing care to a parent with dementia differ, but little is known about how mixed-gender siblings share their caregiving responsibilities or how sharing affects their relationship. This study aimed to explore mixed-gender siblings processes for distributing caregiving tasks when caring for a parent with dementia and the impact of sharing care on their relationship. This descriptive qualitative study recruited fourteen English-speaking mixed-gender sibling pairs caring for a parent with dementia. Online open-ended surveys and individual semi-structured interviews were completed. Interviews and surveys explored division of caregiving responsibilities, conflict resolution, and the effects of sharing care on sibling relationships. Thematic analysis was used to analyze the qualitative data. Five themes were identified: goal of shared caregiving is to meet parents’ needs, sisters often take the lead, practical issues affect sharing of caregiving activities, personal resources or skills affect division of responsibilities, and shared caregiving influences relationship quality. Understanding how siblings share caregiving responsibilities can inform the practices of healthcare professionals who care for people with dementia and their family caregivers.

Familial Mortality Risks in Patients With Ischemic Stroke: A Swedish Sibling Study.

The influence of familial factors on the prognosis of ischemic stroke (IS) is unknown. This nationwide follow-up study evaluated familial mortality risks of IS among Swedish sibling pairs hospitalized for IS. We linked Swedish nationwide registers for the identification of 1380 Swedish born sibling pairs (2760 cases), where both siblings were hospitalized for first-time IS between 1991 and 2010. Median age was 62 years (range, 26-78 years). Sibling pairs with cancer were excluded. Familial hazard ratios (FHRs) for mortality after first IS hospitalization were determined with Cox regression. The influence of proband survival after IS was categorized as short sibling survival (<1, 2, 3, 4, or 5 years) or long sibling survival (≥1, 2, 3, 4, or 5 years) after IS. FHRs were adjusted for age at onset, sex, education, county, year of diagnosis, days of hospitalization, and comorbidities. Short sibling survival (ie, <3 or <4 years) after IS was associated with an adjusted FHR of 1.29 (95% CI, 1.05-1.58) and 1.24 (95% CI, 1.02-1.51), respectively, for overall mortality after IS. Stratified analysis showed that short sibling survival (ie, <2-<5 years) was stronger and significant only among younger individuals (<62 years) and males. Highest FHR for short sibling survival (ie, <4 years) was 1.42 (95% CI, 1.08-1.88) for younger individuals and 1.50 (95% CI, 1.21-1.87) for males. For young male subjects, FHR was 1.80 (95% CI, 1.33-2.46). In the adjusted model, mortality was also associated with sex, education, age at onset, year of diagnosis, days of hospitalization, coronary heart disease, diabetes, dementia, heart failure, obesity, alcoholism, and hyperlipidemia. Our results suggest that family history of short survival in siblings after IS is associated with mortality after IS for younger male subjects. Additional studies are needed to characterize possible genetic and nongenetic familial environmental causes of this association.

Timing is everything: Clinical courses of Hunter syndrome associated with age at initiation of therapy in a sibling pair

Hunter syndrome, or mucopolysaccharidosis (MPS) II, is a rare lysosomal disorder characterized by progressive, multi-system disease. As most symptoms cannot be reversed once established, early detection and treatment prior to the onset of clinical symptoms are critical. However, it is difficult to identify affected individuals early in disease, and therefore the long-term outcomes of initiating treatment during this optimal time period are incompletely described. We report long-term clinical outcomes of treatment when initiated prior to obvious clinical signs by comparing the courses of two siblings with neuronopathic Hunter syndrome (c.1504 T > G[p.W502G]), one who was diagnosed due to clinical disease (Sibling-O, age 3.7 years) and the other who was diagnosed before disease was evident (Sibling-Y, age 12 months), due to his older sibling's findings. The brothers began enzyme replacement therapy within a month of diagnosis. Around the age of 5 years, Sibling-O had a cognitive measurement score in the impaired range of <55 (average range 85–115), whereas Sibling-Y at this age received a score of 91. Sibling-O has never achieved toilet training and needs direct assistance with toileting, dressing, and washing, while Sibling-Y is fully toilet-trained and requires less assistance with daily activities. Both siblings have demonstrated sensory-seeking behaviors, hyperactivity, impulsivity, and sleep difficulties; however, Sibling-O demonstrates physical behaviors that his brother does not, namely biting, pushing, and frequent elopement. Since the time of diagnosis, Sibling-O has had significant joint contractures and a steady deterioration in mobility leading to the need for an adaptive stroller at age 11, while Sibling-Y at age 10.5 could hike more than 6 miles without assistance. After nearly a decade of therapy, there were more severe and life-limiting disease manifestations for Sibling-O; data from caregiver interview indicated substantial differences in Quality of Life for the child and the family, dependent on timing of ERT. The findings from this sibling pair provide evidence of superior somatic and neurocognitive outcomes associated with presymptomatic treatment of Hunter syndrome, aligned with current considerations for newborn screening.

Timing is everything in Hunter syndrome: Differential clinical courses associated with age at initiation of therapy in a sibling pair

Timing is everything in Hunter syndrome: Differential clinical courses associated with age at initiation of therapy in a sibling pair

A Hunter syndrome sibling pair: Differential effects of age at initiation of enzyme replacement therapy on growth, orthopedic disease, and daily living skills

A Hunter syndrome sibling pair: Differential effects of age at initiation of enzyme replacement therapy on growth, orthopedic disease, and daily living skills

Inherited and de novo variants extend the etiology of TAOK1-associated neurodevelopmental disorder

Alterations in the TAOK1 gene have recently emerged as the cause of developmental delay with or without intellectual impairment or behavioral abnormalities (MIM # 619575). The 32 cases currently described in the literature have predominantly de novo alterations in TAOK1 and a wide spectrum of neurodevelopmental abnormalities. Here, we report four patients with novel pathogenic TAOK1 variants identified by research genome sequencing, clinical exome sequencing, and international matchmaking. The overlapping clinical features of our patients are consistent with the emerging core phenotype of TAOK1-associated syndrome: facial dysmorphism, feeding difficulties, global developmental delay, joint laxity, and hypotonia. However, behavioral abnormalities and gastrointestinal issues are more common in our cohort than previously reported. Two patients have de novo TAOK1 variants (one missense, one splice site) consistent with most known alterations in this gene. However, we also report the first sibling pair who both inherited a TAOK1 frameshift variant from a mildly affected mother. Our findings suggest that incomplete penetrance and variable expressivity are relatively common in TAOK1-associated syndrome, which holds important implications for clinical genetic testing.

Association of Preeclampsia and Perinatal Complications With Offspring Neurodevelopmental and Psychiatric Disorders

Maternal preeclampsia has been reported to increase the risk of autism spectrum disorder, attention-deficit/hyperactivity disorder (ADHD), and intellectual disability in offspring. However, the association between maternal preeclampsia combined with perinatal complications and neurodevelopmental and psychiatric disorders in offspring is less well documented. To examine the association of maternal preeclampsia, separately and together with perinatal complications, with neurodevelopmental and psychiatric disorders in offspring. This population-based cohort study used data from nationwide registries in Finland to assess all singleton live births (N = 1 012 723) between January 1, 1996, and December 31, 2014. Offspring were followed up until December 31, 2018 (when the oldest reached age 22 years). Exclusion criteria were maternal inpatient psychiatric diagnoses and pregestational diabetes. The study and data analysis were conducted from May 1, 2020, to June 1, 2021. Preeclampsia and perinatal complications (delivery earlier than 34 weeks' gestation and/or small for gestational age). The primary outcomes were neurodevelopmental and psychiatric diagnoses and dispensation of psychotropic drugs among offspring until December 31, 2018. Cox proportional hazards regression analyses were performed to assess the associations. Of 1 012 723 singleton live births (51.1% boys; mean [SD] maternal age at birth, 30.0 [5.4] years; specific data on race and ethnicity were not available in the data set), 21 010 children (2.1%) were exposed to preeclampsia alone, 33 625 children (3.3%) were exposed to perinatal complications alone, and 4891 children (0.5%) were exposed to both preeclampsia and perinatal complications. A total of 93 281 children (9.2%) were diagnosed with a neurodevelopmental or psychiatric disorder. Offspring exposed to both preeclampsia and perinatal complications had an increased risk of any neurodevelopmental or psychiatric disorder after adjusting for potential confounding (adjusted hazard ratio [aHR], 2.11; 95% CI, 1.96-2.26) compared with those not exposed to either preeclampsia or perinatal complications; this risk was higher than exposure to either preeclampsia alone (aHR, 1.18; 95% CI, 1.12-1.23) or perinatal complications alone (aHR, 1.77; 95% CI, 1.72-1.82). Sibling pair analyses did not detect any increase in the risk of neurodevelopmental or psychiatric disorders after exposure to preeclampsia alone, but offspring exposed to both preeclampsia and perinatal complications had increased risks of intellectual disabilities (aHR, 3.24; 95% CI, 1.05-10.06), specific developmental disorders (aHR, 3.56; 95% CI, 2.35-5.41), ADHD and conduct disorders (aHR, 2.42; 95% CI, 1.09-5.39), and other behavioral and emotional disorders (aHR, 2.45; 95% CI, 1.17-5.13). The risk estimates for specific developmental disorders (aHR, 2.82; 95% CI, 2.60-3.05) and ADHD and conduct disorders (aHR, 1.88; 95% CI, 1.65-2.14) were higher among offspring exposed to both preeclampsia and perinatal complications compared with those exposed to perinatal complications alone (aHR, 2.26 [95% CI, 2.18-2.33] and 1.60 [95% CI, 1.52-1.68], respectively). In this study, exposure to both maternal preeclampsia and perinatal complications was associated with intellectual disabilities, specific developmental disorders, ADHD and conduct disorders, and other behavioral and emotional disorders in offspring. For specific developmental disorders and ADHD and conduct disorders, the risk estimates were higher among offspring exposed to both preeclampsia and perinatal complications compared with those exposed to perinatal complications only.

Intrafamilial phenotypic variability in TBC1D24-TLDc homozygous pathogenic variant-related developmental and epileptic encephalopathy

ObjectiveTo describe intrafamilial phenotypic variability in rare TBC1D24-TLDc homozygous pathogenic variant-related developmental and epileptic encephalopathy (DEE). MethodsFour individuals from two unrelated families who had been diagnosed with DEE caused by TBC1D24-TLDc homozygous c.1499C>T (p.A500V) pathogenic variant were recruited. ResultsThe age of seizure onset ranged from 1 to 7 months. All four individuals exhibited very prolonged multifocal myoclonus or focal clonic fits, and the interictal EEGs were prone to dissociation with clinical seizures. The common precipitating factors for seizures were viral infection and fever. Two individuals from family II had progressive cerebellar atrophy: one had ataxia and the other one had no cerebellar signs clinically. All individuals had pharmaco-resistant epilepsy. However, the younger siblings of the two sibling pairs had normal neurodevelopmental outcomes. ConclusionIntrafamilial phenotypic variability of cerebellar neurodegeneration on neuroimages and neurodevelopmental outcomes might be noted in individuals with TBC1D24-TLDc homozygous c.1499C>T (p.A500V) pathogenic variant-related DEE.

Sibling Resemblances in Physical Fitness in Three Distinct Regions in Peru: The Peruvian Sibling Study on Growth and Health.

We estimated sibling resemblance in health-related physical fitness (PF) and examined how individual characteristics and shared natural environment accounted for sibling similarities. The sample comprised 656 sibling pairs and 102 triplets (6-15years of age), from three geographical areas of Peru. PF components included morphological (waist circumference, sum of skinfolds), muscular (handgrip strength, standing long jump), and motor (shuttle-run). Body mass index (BMI) and somatic maturation were also assessed. In general, sibling intraclass correlations differed significantly across sib-ship types for waist circumference and handgrip strength but were the same for sum of skinfolds, standing long jump, and shuttle-run. Further, in general, both individual characteristics and geographical area of residence significantly influenced the magnitude of sibling resemblance as well as the mean levels of PF. In conclusion, individual characteristics and shared natural environment jointly influenced the expression of PF in Peruvian siblings, revealing the importance of these features when designing individualized programs promoting fitness.

Indirect Genetic Effects of ADIPOQ Variants on Lipid Levels in a Sibling Study of a Rural Chinese Population

Variations in lipid levels are the result of combinations of genetic and environmental factors. We aim to investigate the indirect effect between siblings of the three polymorphisms of ADIPOQ on serum lipid levels in rural Chinese populations. A total of 2571 sibling pairs were enrolled as study participants. A generalized estimating equation was used to accommodate a family-based design. We used stratified analysis to detect sex combination differences in the indirect genetic effect. We found a significant association between the number of altered risk alleles of rs182052 and ego lipid levels of TG (β = 0.177, P = 0.003), TC (β = 0.140, P = 0.004) and LDL-C (β = 0.098, P = 0.014). Ego and altered genotypes of rs182052 demonstrated a joint effect on ego lipid levels of TC (β = 0.212, P = 0.019), HDL-C (β = 0.099, P = 0.002) and LDL-C (β = 0.177, P = 0.013) in recessive inheritance mode. In opposite-sex siblings, the altered GG genotype of rs182052 increased the ego lipid levels. Thus, our findings demonstrate that ADIPOQ has an indirect genetic effect on lipid levels in sibling pairs, and there are sex-combination differences in the indirect genetic effect in siblings.

Analysis of clinical features and pathogenic variants in a Chinese pedigree affected with congenital glycosylation disease

To explore the clinical features and genetic basis for a Chinese pedigree diagnosed with congenital glycosylation disease (CGD). Clinical manifestations of two brothers were analyzed. Whole exome sequencing was carried out for the sib pair. Suspected variants were verified by Sanger sequencing. Both the proband and her younger brother were found to carry compound heterozygous variants of the PMM2 gene, which included a known pathogenic mutation of c.395T>C (p.I132T) and a previously unreported c.448-1(delAG) in the 5' end of exon 6 of the gene. The compound heterozygous variants of the PMM2 gene probably underlay the CGD in the sib pair.

Estimating sibling spillover effects with unobserved confounding using gain-scores

A growing area of research in epidemiology is the identification of health-related sibling spillover effects, or the effect of one individual's exposure on their sibling's outcome. The health within families may be confounded by unobserved factors, rendering identification of sibling spillovers challenging. We demonstrate a gain-score (fixed effects) regression method for identifying exposure-to-outcome spillover effects within sibling pairs in linear models. The method identifies the exposure-to-outcome spillover effect if only one sibling's exposure affects the other's outcome, and it identifies the difference between the spillover effects if both siblings' exposures affect the others' outcomes. The method fails with outcome-to-exposure spillover or with outcome-to-outcome spillover. Analytic results, Monte Carlo simulations, and a brief application demonstrate the method and its limitations. We estimate the spillover effect of a child's preterm birth on an older sibling's literacy skills, measured by the Phonological Awareness Literacy Screening-Kindergarten test. We analyze 20,010 sibling pairs from a population-wide, Wisconsin-based (United States) birth cohort. Without covariate adjustment, we estimate that preterm birth modestly decreases an older sibling's test score. Gain-scores are a promising strategy for identifying exposure-to-outcome spillover effects in sibling pairs while controlling for sibling-invariant unobserved confounding.

Development of Osteomyelitis of the Jaw in Patients with Congenital Insensitivity to Pain with Anhidrosis: A Case Study in a Sibling Pair

Development of Osteomyelitis of the Jaw in Patients with Congenital Insensitivity to Pain with Anhidrosis: A Case Study in a Sibling Pair

ЛОКУС КОНТРОЛЯ В СИСТЕМЕ ЛИЧНОСТНЫХ ХАРАКТЕРИСТИК МОЛОДЕЖИ: СИБЛИНГОВЫЙ КОНТЕКСТ

On a sample of siblings at the age of early adulthood, the structure of links between the locus of control and other psychological characteristics is considered. The sample included 106 pairs of siblings (212 respondents in total) with an age difference of no more than 5 years; the average age of the older sibling is 24.51 ± 4.56, the younger one is 21.73 ± 4.17 full years. Each member of the sibling couple completed 5 questionnaires: Level of Subjective Control, Short Big Five Portrait Inventory, Short Version of the Uncertainty Tolerance Inventory, Short Version of the Sensation Seeking Inventory, and the Dirty Dozen Inventory. The data obtained during the study are studied in two subgroups - older and younger siblings of each pair. It was revealed that, on average, older and younger siblings do not differ from each other in the localization of control over significant events for themselves, both in life in general and in particular specific situations (health status, achievements, failures, family, workplace and interpersonal relationships). At the same time, the study of the structure of the links between the level of subjective control and other psychological characteristics in the groups of older and younger reveals a number of differences.

Expression of Hey marks a subset of enteroendocrine cells in the Drosophila embryonic and larval midgut.

Hey is a conserved transcription factor of the bHLH-Orange family that participates in the response to Notch signaling in certain tissues. Whereas three Hey paralogues exist in mammalian genomes, Drosophila possesses a single Hey gene. Fly Hey is expressed in the subset of newborn neurons that receive a Notch signal to differentiate them from their sibling cells after the asymmetric division of precursors called ganglion-mother-cells. We used a polyclonal anti-Hey serum and a GFP-tagged transgenic duplication of the Hey locus to examine its expression in tissues outside the nervous system in embryos and larvae. We detected robust Hey expression in the embryonic midgut primordium at the time of birth of enteroendocrine cells, identified by expression of Prospero. Approximately half of the Pros-positive cells were also Hey positive at mid-embryogenesis. By the end of embryogenesis, most enteroendocrine cells had downregulated Hey expression, although it was still detectable at low levels after hatching. Low levels of Hey were also detected in subsets of the epithelial enterocytes at different times. Embryo enteroendocrine Hey expression was found to be Notch dependent. In late third-instar larvae, when few new enteroendocrine cells are born, novel Hey expression was detected in one cell of each sibling pair. In conclusion, Hey is strongly expressed in one of each pair of newly-born enteroendocrine cells. This is consistent with a hypothesis that embryonic enteroendocrine cells are born by an asymmetric division of a precursor, where Notch/Hey probably distinguish between the subtypes of these cells upon their differentiation.