Why do sex chromosomes progressively lose recombination?

Progressive recombination loss is a common feature of sex chromosomes. Yet, the evolutionary drivers of this phenomenon remain a mystery. For decades, differences in trait optima between sexes (sexual antagonism) have been the favoured hypothesis, but convincing evidence is lacking. Recent years have seen a surge of alternative hypotheses to explain progressive extensions and maintenance of recombination suppression: neutral accumulation of sequence divergence, selection of nonrecombining fragments with fewer deleterious mutations than average, sheltering of recessive deleterious mutations by linkage to heterozygous alleles, early evolution of dosage compensation, and constraints on recombination restoration. Here, we explain these recent hypotheses and dissect their assumptions, mechanisms, and predictions. We also review empirical studies that have brought support to the various hypotheses.

Sheltering of deleterious mutations explains the stepwise extension of recombination suppression on sex chromosomes and other supergenes.

Many organisms have sex chromosomes with large nonrecombining regions that have expanded stepwise, generating "evolutionary strata" of differentiation. The reasons for this remain poorly understood, but the principal hypotheses proposed to date are based on antagonistic selection due to differences between sexes. However, it has proved difficult to obtain empirical evidence of a role for sexually antagonistic selection in extending recombination suppression, and antagonistic selection has been shown to be unlikely to account for the evolutionary strata observed on fungal mating-type chromosomes. We show here, by mathematical modeling and stochastic simulation, that recombination suppression on sex chromosomes and around supergenes can expand under a wide range of parameter values simply because it shelters recessive deleterious mutations, which are ubiquitous in genomes. Permanently heterozygous alleles, such as the male-determining allele in XY systems, protect linked chromosomal inversions against the expression of their recessive mutation load, leading to the successive accumulation of inversions around these alleles without antagonistic selection. Similar results were obtained with models assuming recombination-suppressing mechanisms other than chromosomal inversions and for supergenes other than sex chromosomes, including those without XY-like asymmetry, such as fungal mating-type chromosomes. However, inversions capturing a permanently heterozygous allele were found to be less likely to spread when the mutation load segregating in populations was lower (e.g., under large effective population sizes or low mutation rates). This may explain why sex chromosomes remain homomorphic in some organisms but are highly divergent in others. Here, we model a simple and testable hypothesis explaining the stepwise extensions of recombination suppression on sex chromosomes, mating-type chromosomes, and supergenes in general.

The genomes of Darwin's primroses reveal chromosome-scale adaptive introgression and differential permeability of species boundaries.

Introgression is an important source of genetic variation that can determine species adaptation to environmental conditions. Yet, definitive evidence of the genomic and adaptive implications of introgression in nature remains scarce. The widespread hybrid zones of Darwin's primroses (Primula elatior, Primula veris, and Primula vulgaris) provide a unique natural laboratory for studying introgression in flowering plants and the varying permeability of species boundaries. Through analysis of 650 genomes, we provide evidence of an introgressed genomic region likely to confer adaptive advantage in conditions of soil toxicity. We also document unequivocal evidence of chloroplast introgression, an important precursor to species-wide chloroplast capture. Finally, we provide the first evidence that the S-locus supergene, which controls heterostyly in primroses, does not introgress in this clade. Our results contribute novel insights into the adaptive role of introgression and demonstrate the importance of extensive genomic and geographical sampling for illuminating the complex nature of species boundaries.

The interplay of local adaptation and gene flow may lead to the formation of supergenes.

Supergenes are genetic architectures resulting in the segregation of alternative combinations of alleles underlying complex phenotypes. The co-segregation of alleles at linked loci is often facilitated by polymorphic chromosomal rearrangements suppressing recombination locally. Supergenes are involved in many complex polymorphisms, including sexual, colour or behavioural polymorphisms in numerous plants, fungi, mammals, fish, and insects. Despite a long history of empirical and theoretical research, the formation of supergenes remains poorly understood. Here, using a two-island population genetic model, we explore how gene flow and the evolution of overdominant chromosomal inversions may jointly lead to the formation of supergenes. We show that the evolution of inversions in differentiated populations, both under disruptive selection, leads to an increase in frequency of poorly adapted, immigrant haplotypes. Indeed, rare allelic combinations, such as immigrant haplotypes, are more frequently reshuffled by recombination than common allelic combinations, and therefore benefit from the recombination suppression generated by inversions. When an inversion capturing a locally adapted haplotype spreads but is associated with a fitness cost hampering its fixation (e.g. a recessive mutation load), the maintenance of a non-inverted haplotype in the population is enhanced; under certain conditions, the immigrant haplotype persists alongside the inverted local haplotype, while the standard local haplotype disappears. This establishes a stable, local polymorphism with two non-recombining haplotypes encoding alternative adaptive strategies, that is, a supergene. These results bring new light to the importance of local adaptation, overdominance, and gene flow in the formation of supergenes and inversion polymorphisms in general.

Tempo of Degeneration Across Independently Evolved Nonrecombining Regions.

Recombination is beneficial over the long term, allowing more effective selection. Despite long-term advantages of recombination, local recombination suppression can evolve and lead to genomic degeneration, in particular on sex chromosomes. Here, we investigated the tempo of degeneration in nonrecombining regions, that is, the function curve for the accumulation of deleterious mutations over time, leveraging on 22 independent events of recombination suppression identified on mating-type chromosomes of anther-smut fungi, including newly identified ones. Using previously available and newly generated high-quality genome assemblies of alternative mating types of 13 Microbotryum species, we estimated degeneration levels in terms of accumulation of nonoptimal codons and nonsynonymous substitutions in nonrecombining regions. We found a reduced frequency of optimal codons in the nonrecombining regions compared with autosomes, that was not due to less frequent GC-biased gene conversion or lower ancestral expression levels compared with recombining regions. The frequency of optimal codons rapidly decreased following recombination suppression and reached an asymptote after ca. 3 Ma. The strength of purifying selection remained virtually constant at dN/dS = 0.55, that is, at an intermediate level between purifying selection and neutral evolution. Accordingly, nonsynonymous differences between mating-type chromosomes increased linearly with stratum age, at a rate of 0.015 per My. We thus develop a method for disentangling effects of reduced selection efficacy from GC-biased gene conversion in the evolution of codon usage and we quantify the tempo of degeneration in nonrecombining regions, which is important for our knowledge on genomic evolution and on the maintenance of regions without recombination.

How chromosomal inversions reorient the evolutionary process.

Inversions are structural mutations that reverse the sequence of a chromosome segment and reduce the effective rate of recombination in the heterozygous state. They play a major role in adaptation, as well as in other evolutionary processes such as speciation. Although inversions have been studied since the 1920s, they remain difficult to investigate because the reduced recombination conferred by them strengthens the effects of drift and hitchhiking, which in turn can obscure signatures of selection. Nonetheless, numerous inversions have been found to be under selection. Given recent advances in population genetic theory and empirical study, here we review how different mechanisms of selection affect the evolution of inversions. A key difference between inversions and other mutations, such as single nucleotide variants, is that the fitness of an inversion may be affected by a larger number of frequently interacting processes. This considerably complicates the analysis of the causes underlying the evolution of inversions. We discuss the extent to which these mechanisms can be disentangled, and by which approach.

The Son's Fault: Martin Luther King, Jr.'s Search for and Recovery of Sonship.

This article examines the role of sonship in the psychological and spiritual development of men. In using the methodology of psychobiography, I explore the life history of Martin Luther King, Jr. to analyze his search for and recovery of sonship. I propose that sonship helps men rebel against and, in the end, overcome the feelings of inadequacy that are experienced in their struggles to achieve manhood, particularly within the father-son dyad. The scholarship of pastoral theologian Donald Capps is instructive in this regard, in that he suggests that sons should be allowed to search for a male figure, a father-substitute, who can affirm, not disdain or reject, this state of sonship. In the end, what is often viewed as a negative act of regression-i.e., the recovery of and return to sonship-is recognized instead as a positive one that assists a man in his journey toward wholeness.

Analysis of behavioral change techniques in community-led total sanitation programs.

The lack of sanitation facilitates the spread of diarrheal diseases-a leading cause of child deaths worldwide. As of 2012, an estimated 1 billion people still practiced open defecation (OD). To address this issue, one behavioral change approach used is community-led total sanitation (CLTS). It is now applied in an estimated 66 countries worldwide, and many countries have adopted this approach as their main strategy for scaling up rural sanitation coverage. While it appears that many of the activities used in CLTS-that target community-level changes in sanitation behaviors instead of household-level changes-have evolved out of existing behavior change frameworks and techniques, it is less clear how these activities are adapted by different organizations and applied in different country contexts. The aims of this study are to (i) show which behavior change frameworks and techniques are the most common in CLTS interventions; (ii) describe how activities are implemented in CLTS interventions by region and context; and (3) determine which activities program implementers considered the most valuable in achieving open defecation free (ODF) status and sustaining it. The results indicate that a wide range of activities are conducted across the different programs and often go beyond standard CLTS activities. CLTS practitioners ranked follow-up and monitoring activities as the most important activities for achieving an ODF community, yet only 1 of 10 organizations conducted monitoring and follow-up throughout their project. Empirical studies are needed to determine which specific behavioral change activities are most effective at ending OD and sustaining it.

Improving Craniofacial Team Collaboration: A Multicenter Interview Study of Effective Team Meetings.

Objective: In the USA, the American Cleft Palate Association-Craniofacial Association (ACPA-CPF) specifies guidelines to ensure craniofacial teams function in a multidisciplinary fashion to provide care in a sequence that mirrors the patient's needs. Among these guidelines is the expectation that teams hold regular multidisciplinary team meetings to discuss patient care. The purpose of this study was to identify factors that contribute to optimal team functioning during these meetings. The impact of the virtual format on meetings was also evaluated. Design: One-hour semi-structured interviews of craniofacial team members, queried on current and ideal team meetings, were conducted from December 2020 - January 2021. Interviews were recorded, transcribed, and coded to identify common themes until thematic saturation was achieved. Setting/Participants: Sixteen team members from three major American craniofacial centers were interviewed virtually. Results: Three major categories were identified as integral to successful meetings: (1) meeting content, (2) meeting processes, and (3) team dynamics. Within these categories are several factors that participants reported as important to optimize their multidisciplinary meetings: key content for discussions, integration of patient perspective, recognition of collaboration in determining proper sequence of treatments, an attentive discussion leader promoting equitable discussions, managing absences, and team diversity. Participants also identified benefits and pitfalls of hosting meetings in the virtual setting, including lack of engagement and awkward communication. Conclusion: Diverse groups of disciplines are expected to come together during craniofacial multidisciplinary meetings to formulate intricate care plans for complex patients. In this study, craniofacial team members have identified several key factors to optimize these meetings. The research group used these factors to propose a self-evaluation instrument for meeting quality improvement, provided in printable format. Further studies should evaluate how implementation of these factors affects meetings and ultimately guides patient care.

Repeated loss of function at HD mating-type genes and of recombination suppression without mating-type locus linkage in anther-smut fungi.

A wide diversity of mating systems occur in nature, with frequent evolutionary transitions in mating-compatibility mechanisms. Basidiomycete fungi typically have two mating-type loci controlling mating compatibility, HD and PR, usually residing on different chromosomes. In Microbotryum anther-smut fungi, there have been repeated events of linkage between the two mating-type loci through chromosome fusions, leading to large non-recombining regions. By generating high-quality genome assemblies, we found that two sister Microbotryum species parasitizing Dianthus plants, M. superbum and M. shykoffianum, as well as the distantly related M. scorzonarae, have their HD and PR mating-type loci on different chromosomes, but with the PR mating-type chromosome fused with part of the ancestral HD chromosome. Furthermore, progressive extensions of recombination suppression have generated evolutionary strata. In all three species, rearrangements suggest the existence of a transient stage of HD-PR linkage by whole chromosome fusion, and, unexpectedly, the HD genes lost their function. In M. superbum, multiple natural diploid strains were homozygous, and the disrupted HD2 gene was hardly expressed. Mating tests confirmed that a single genetic factor controlled mating compatibility (i.e. PR) and that haploid strains with identical HD alleles could mate and produce infectious hyphae. The HD genes have therefore lost their function in the control of mating compatibility in these Microbotryum species. While the loss of function of PR genes in mating compatibility has been reported in a few basidiomycete fungi, these are the first documented cases for the loss of mating-type determination by HD genes in heterothallic fungi. The control of mating compatibility by a single genetic factor is beneficial under selfing and can thus be achieved repeatedly, through evolutionary convergence in distant lineages, involving different genomic or similar pathways.

Domain-informed graph neural networks: A quantum chemistry case study.

We explore different strategies to integrate prior domain knowledge into the design of graph neural networks (GNN). Our study is supported by a use-case of estimating the potential energy of chemical systems (molecules and crystals) represented as graphs. We integrate two elements of domain knowledge into the design of the GNN to constrain and regularise its learning, towards higher accuracy and generalisation. First, knowledge on the existence of different types of relations/graph edges (e.g. chemical bonds in our case study) between nodes of the graph is used to modulate their interactions. We formulate and compare two strategies, namely specialised message production and specialised update of internal states. Second, knowledge of the relevance of some physical quantities is used to constrain the learnt features towards a higher physical relevance using a simple multi-task learning (MTL) paradigm. We explore the potential of MTL to better capture the underlying mechanisms behind the studied phenomenon. We demonstrate the general applicability of our two knowledge integrations by applying them to three architectures that rely on different mechanisms to propagate information between nodes and to update node states. Our implementations are made publicly available. To support these experiments, we release three new datasets of out-of-equilibrium molecules and crystals of various complexities.

First chromosome scale genomes of ithomiine butterflies (Nymphalidae: Ithomiini): Comparative models for mimicry genetic studies.

The ithomiine butterflies (Nymphalidae: Danainae) represent the largest known radiation of Müllerian mimetic butterflies. They dominate by number the mimetic butterfly communities, which include species such as the iconic neotropical Heliconius genus. Recent studies on the ecology and genetics of speciation in Ithomiini have suggested that sexual pheromones, colour pattern and perhaps hostplant could drive reproductive isolation. However, no reference genome was available for Ithomiini, which has hindered further exploration on the genetic architecture of these candidate traits, and more generally on the genomic patterns of divergence. Here, we generated high-quality, chromosome-scale genome assemblies for two Melinaea species, M. marsaeus and M. menophilus, and a draft genome of the species Ithomia salapia. We obtained genomes with a size ranging from 396 to 503 Mb across the three species and scaffold N50 of 40.5 and 23.2 Mb for the two chromosome-scale assemblies. Using collinearity analyses we identified massive rearrangements between the two closely related Melinaea species. An annotation of transposable elements and gene content was performed, as well as a specialist annotation to target chemosensory genes, which is crucial for host plant detection and mate recognition in mimetic species. A comparative genomic approach revealed independent gene expansions in ithomiines and particularly in gustatory receptor genes. These first three genomes of ithomiine mimetic butterflies constitute a valuable addition and a welcome comparison to existing biological models such as Heliconius, and will enable further understanding of the mechanisms of adaptation in butterflies.

The double game of chromosomal inversions in a neotropical butterfly.

Over a century after the first description of a polymorphism controlled by a supergene, these genetic architectures still puzzle biologists. Supergenes are groups of tightly linked loci facilitating the co-segregation of combinations of alleles underlying alternative, complex adaptive strategies. The suppression of recombination at supergenes is generally caused by polymorphic chromosomal rearrangements, such as inversions. The existence of inversion polymorphisms and supergene raises theoretical and empirical questions. Why do these architectures evolve? How can alternative combinations of alleles be formed? How and why is polymorphism maintained? The purpose of this paper is to provide answers to these questions by reviewing recent advances in the study of Heliconius numata, an Amazonian butterfly displaying a striking diversity of wing color patterns. In a broad context, this review highlights mechanisms that play an important role in the evolution of new genomic architecture and in the adaptation of species.

Plus d'un siècle après la première description d'un polymorphisme contrôlé par un supergène, cette architecture génétique interroge toujours les biologistes. Les supergènes sont des groupes de locus étroitement liés qui facilitent la co-ségrégation de combinaisons d'allèles qui, ensemble, sous-tendent différentes stratégies adaptatives complexes. La suppression de la recombinaison au niveau des supergènes est généralement causée par des polymorphismes de réarrangements chromosomiques, tels que les inversions. L'existence de polymorphismes d'inversion et de supergènes soulève des questions théoriques et empiriques. Pourquoi ces architectures évoluent-elles ? Comment des combinaisons alternatives d'allèles peuvent-elles être formées ? Comment et pourquoi le polymorphisme est-il maintenu ? L'objectif de cet article est d'apporter des réponses à ces questions en passant en revue quelques découvertes récentes dans l'étude de Heliconius numata, un papillon amazonien présentant une grande diversité de motifs de couleurs d'ailes. Dans un contexte plus large, cette synthèse met en évidence les mécanismes qui jouent un rôle important dans l'évolution de nouvelles architectures génomiques et dans l'adaptation des espèces.

Association mapping of colour variation in a butterfly provides evidence that a supergene locks together a cluster of adaptive loci.

Supergenes are genetic architectures associated with discrete and concerted variation in multiple traits. It has long been suggested that supergenes control these complex polymorphisms by suppressing recombination between sets of coadapted genes. However, because recombination suppression hinders the dissociation of the individual effects of genes within supergenes, there is still little evidence that supergenes evolve by tightening linkage between coadapted genes. Here, combining a landmark-free phenotyping algorithm with multivariate genome-wide association studies, we dissected the genetic basis of wing pattern variation in the butterfly Heliconius numata. We show that the supergene controlling the striking wing pattern polymorphism displayed by this species contains several independent loci associated with different features of wing patterns. The three chromosomal inversions of this supergene suppress recombination between these loci, supporting the hypothesis that they may have evolved because they captured beneficial combinations of alleles. Some of these loci are, however, associated with colour variations only in a subset of morphs where the phenotype is controlled by derived inversion forms, indicating that they were recruited after the formation of the inversions. Our study shows that supergenes and clusters of adaptive loci in general may form via the evolution of chromosomal rearrangements suppressing recombination between co-adapted loci but also via the subsequent recruitment of linked adaptive mutations. This article is part of the theme issue 'Genomic architecture of supergenes: causes and evolutionary consequences'.

The genome sequence of the scarce swallowtail, Iphiclides podalirius.

The scarce swallowtail, Iphiclides podalirius (Linnaeus, 1758), is a species of butterfly in the family Papilionidae. Here, we present a chromosome-level genome assembly for Iphiclides podalirius as well as gene and transposable element annotations. We investigate how the density of genomic features differs between the 30 Iphiclides podalirius chromosomes. We find that shorter chromosomes have higher heterozygosity at four-fold-degenerate sites and a greater density of transposable elements. While the first result is an expected consequence of differences in recombination rate, the second suggests a counter-intuitive relationship between recombination and transposable element evolution. This high-quality genome assembly, the first for any species in the tribe Leptocircini, will be a valuable resource for population genomics in the genus Iphiclides and comparative genomics more generally.

Mutation load at a mimicry supergene sheds new light on the evolution of inversion polymorphisms.

Chromosomal inversions are ubiquitous in genomes and often coordinate complex phenotypes, such as the covariation of behavior and morphology in many birds, fishes, insects or mammals1-11. However, why and how inversions become associated with polymorphic traits remains obscure. Here we show that despite a strong selective advantage when they form, inversions accumulate recessive deleterious mutations that generate frequency-dependent selection and promote their maintenance at intermediate frequency. Combining genomics and in vivo fitness analyses in a model butterfly for wing-pattern polymorphism, Heliconius numata, we reveal that three ecologically advantageous inversions have built up a heavy mutational load from the sequential accumulation of deleterious mutations and transposable elements. Inversions associate with sharply reduced viability when homozygous, which prevents them from replacing ancestral chromosome arrangements. Our results suggest that other complex polymorphisms, rather than representing adaptations to competing ecological optima, could evolve because chromosomal rearrangements are intrinsically prone to carrying recessive harmful mutations.

Management of noncleft velopharyngeal insufficiency.

PURPOSE OF REVIEW: Velopharyngeal insufficiency in the absence of an overt cleft-palate is a less common and often missed cause of a resonance disorder. The purpose of this manuscript is to provide the reader with an overview of the clinical assessment. Highlight the need for multidisciplinary involvement. Discuss the process of decision-making related to a repair and finally comment on the preoperative, intra-operative, and postoperative considerations. RECENT FINDINGS: With the advent of small calibre videonasendoscopes, evaluation of the size, location, and closure pattern of the velopharyngeal gap has improved the surgeons' ability to provide a tailored repair. Evolutions in technique including posterior pharyngeal wall augmentation and buccal flap advancement in palatal lengthening have all increased the options available to the patient and treating team. SUMMARY: Multidisciplinary assessment by trained specialist from speech and language pathology and surgery remain the cornerstone in the evaluation and management of this patient cohort. Many have a chromosomal anomaly that should be tested for and managed accordingly. These patients are often diagnosed late and have developed additional compensatory speech disorders that often need to be addressed following repair of the palate. Targeted thoughtful assessment will allow for a greater likelihood of successful repair.

Dysregulated TP53 Among PTSD Patients Leads to Downregulation of miRNA let-7a and Promotes an Inflammatory Th17 Phenotype.

Post-traumatic stress disorder (PTSD) is a psychiatric disorder and patients diagnosed with PTSD often express other comorbid health issues, particularly autoimmune and inflammatory disorders. Our previous reports investigating peripheral blood mononuclear cells (PBMCs) from PTSD patients showed that these patients exhibit an increased inflammatory T helper (Th) cell phenotype and widespread downregulation of microRNAs (miRNAs), key molecules involved in post-transcriptional gene regulation. A combination of analyzing prior datasets on gene and miRNA expression of PBMCs from PTSD and Control samples, as well as experiments using primary PBMCs collected from human PTSD and Controls blood, was used to evaluate TP53 expression, DNA methylation, and miRNA modulation on Th17 development. In the current report, we note several downregulated miRNAs were linked to tumor protein 53 (TP53), also known as p53. Expression data from PBMCs revealed that compared to Controls, PTSD patients exhibited decreased TP53 which correlated with an increased inflammatory Th17 phenotype. Decreased expression of TP53 in the PTSD population was shown to be associated with an increase in DNA methylation in the TP53 promotor region. Lastly, the most significantly downregulated TP53-associated miRNA, let-7a, was shown to negatively regulate Th17 T cells. Let-7a modulation in activated CD4+ T cells was shown to influence Th17 development and function, via alterations in IL-6 and IL-17 production, respectively. Collectively, these studies reveal that PTSD patients could be susceptible to inflammation by epigenetic dysregulation of TP53, which alters the miRNA profile to favor a proinflammatory Th17 phenotype.

Patient-Reported Outcomes after Intensity-Modulated Proton Therapy for Oropharynx Cancer.

PURPOSE: To report patient-reported outcomes (PROs) derived from the Functional Assessment of Cancer Therapy-Head and Neck (FACT-HN) tool, in patients with oropharynx cancer (OPC) treated with intensity-modulated proton therapy (IMPT) in the context of first-course irradiation. MATERIALS AND METHODS: Patients with locally advanced OPC treated with radical IMPT between 2011 and 2018 were included in a prospective registry. FACT-HN scores were measured serially during and 24 months following IMPT. PRO changes in the FACT-HN scores over time were assessed with mixed-model analysis. RESULTS: Fifty-seven patients met inclusion criteria. Median age was 60 years (range, 41-84), and 91% had human papillomavirus-associated disease. In total, 28% received induction chemotherapy and 68% had concurrent chemotherapy. Compliance to FACT-HN questionnaire completion was 59%, 48%, and 42% at 6, 12, and 24 months after treatment, respectively. The mean FACT-General (G), FACT-Total, and FACT-Trial Outcome Index (TOI) score changes were statistically and clinically significant relative to baseline from week 3 of treatment up to week 2 after treatment. Nadir was reached at week 6 of treatment for all scores, with maximum scores dropping by 15%, 20%, and 39% compared to baseline for FACT-G, FACT-Total, and FACT-TOI, respectively. Subdomain scores of physical well-being, functional well-being, and head and neck additional concerns decreased from baseline during treatment and returned to baseline at week 4 after treatment. CONCLUSIONS: IMPT was associated with a favorable PRO trajectory, characterized by an acute decline followed by rapid recovery to baseline. This study establishes the expected acute, subacute, and chronic trajectory of PROs for patients undergoing IMPT for OPC.

Fiberoptic Endoscopic Evaluation of Swallowing in Infants and Children: Protocol, Safety, and Clinical Efficacy: 25 Years of Experience.

BACKGROUND: The application of fiberoptic endoscopic evaluation of swallowing (FEES) in the pediatric dysphagia protocol requires specialized knowledge of pediatric conditions that result in dysphagia, recognition of normal and abnormal laryngopharyngeal anatomy and function across ages, and the ability to identify maturational changes in anatomy and function of the aerodigestive tract that pertain to airway protection and swallowing function. METHODS: Over the past 25 years, we have performed over 7,000 collaborative Otolaryngology and Speech-Language Pathology FEES examinations in patients ranging from 2 days of age to young adults. During this time period, we have monitored the safety of the procedure, explored the feasibility and utility of FEES across conditions, compared and contrasted FEES to the videofluoroscopic evaluation of swallowing (VFSS), and developed specific pediatric FEES protocols with operational definitions for identification and interpretation of swallowing parameters. RESULTS: FEES has proved to be a safe procedure in patients across ages. There have been no significant adverse events. FEES is comparable to the VFSS in the assessment of events before and after the swallow. It provides unique information regarding laryngopharyngeal anatomy and function, airway protection integrity, sensory threshold, and secretion management ability, as well as pharyngeal swallowing dynamics and the efficacy of compensatory swallowing strategies. CONCLUSIONS: There are specific indications and contraindications for pediatric FEES, and unique components that characterize the pediatric FEES protocols across ages and conditions. FEES procedures performed jointly by an Otolaryngologist and Speech-Language pathologist offer a team approach to interpretation and management recommendations.