Publications

Abstract

Comparative neurobiology allows us to investigate relationships between phylogeny and the brain and understand the evolution of traits. Bats constitute an attractive group of mammalian species for comparative studies, given their large diversity in behavioural phenotypes, brain morphology, and array of specialised traits. Currently, the order Chiroptera contains over 1,450 species within 21 families and spans ca. 65 million years of evolution. To date, 194 Neotropical bat species (ca. 13% of the total number of species around the world) have been recorded in Central America. This study includes qualitative and quantitative macromorphological descriptions of the brains of 12 species from six families of Neotropical bats. These analyses, which include histological neuronal staining of two species from different families (Phyllostomus hastatus and Saccopteryx bilineata), show substantial diversity in brain macromorphology including brain shape and size, exposure of mesencephalic regions, and cortical and cerebellar fissure depth. Brain macromorphology can in part be explained by phylogeny as species within the same family are more similar to each other. However, macromorphology cannot be explained by evolutionary time alone as brain differences between some phyllostomid bats are larger than between species from the family Emballonuridae despite being of comparable diverging distances in the phylogenetic tree. This suggests that faster evolutionary changes in brain morphology occurred in phyllostomids — although a larger number of species needs to be studied to confirm this. Our results show the rich diversity in brain morphology that bats provide for comparative and evolutionary studies.

Abstract

We present a reference genome assembly from an individual male Rhynchonycteris naso (Chordata; Mammalia; Chiroptera; Emballonuridae). The genome sequence is 2.46 Gb in span. The majority of the assembly is scaffolded into 22 chromosomal pseudomolecules, with the Y sex chromosome assembled.

Abstract

We describe here the first characterization of the genome of the bat Pteronotus mexicanus, an endemic species of Mexico, as part of the Mexican Bat Genome Project which focuses on the characterization and assembly of the genomes of endemic bats in Mexico. The genome was assembled from a liver tissue sample of an adult male from Jalisco, Mexico provided by the Texas Tech University Museum tissue collection. The assembled genome size was 1.9 Gb. The assembly of the genome was fitted in a framework of 110,533 scaffolds and 1,659,535 contigs. The ecological importance of bats such as P. mexicanus, and their diverse ecological roles, underscores the value of having complete genomes in addressing information gaps and facing challenges regarding their function in ecosystems and their conservation.

Abstract

Comparative studies of vocal learning and vocal non-learning animals can increase our understanding of the neurobiology and evolution of vocal learning and human speech. Mammalian vocal learning is understudied: most research has either focused on vocal learning in songbirds or its absence in non-human primates. Here we focus on a highly promising model species for the neurobiology of vocal learning: grey seals. We provide a neuroanatomical atlas (based on dissected brain slices and magnetic resonance images), a labelled MRI template, a 3D model with volumetric measurements of brain regions, and histological cortical stainings. Four main features of the grey seal brain stand out. (1) It is relatively big and highly convoluted. (2) It hosts a relatively large temporal lobe and cerebellum, structures which could support developed timing abilities and acoustic processing. (3) The cortex is similar to humans in thickness and shows the expected six-layered mammalian structure. (4) Expression of FoxP2 - a gene involved in vocal learning and spoken language - is present in deeper layers of the cortex. Our results could facilitate future studies targeting the neural and genetic underpinnings of mammalian vocal learning, thus bridging the research gap from songbirds to humans and non-human primates.Competing Interest StatementThe authors have declared no competing interest.

Abstract

Human vocal development and speech learning require acoustic feedback, and
humans who are born deaf do not acquire a normal adult speech capacity. Most
other mammals display a largely innate vocal repertoire. Like humans, bats are
thought to be one of the few taxa capable of vocal learning as they can acquire
new vocalizations by modifying vocalizations according to auditory experiences.
We investigated the effect of acoustic deafening on the vocal development of the
pale spear-nosed bat. Three juvenile pale spear-nosed bats were deafened, and
their vocal development was studied in comparison with an age-matched, hear-
ing control group. The results show that during development the deafened bats
increased their vocal activity, and their vocalizations were substantially altered,
being much shorter, higher in pitch, and more aperiodic than the vocalizations
of the control animals. The pale spear-nosed bat relies on auditory feedback
for vocal development and, in the absence of auditory input, species-atypical
vocalizations are acquired. This work serves as a basis for further research
using the pale spear-nosed bat as a mammalian model for vocal learning, and
contributes to comparative studies on hearing impairment across species.
This article is part of the theme issue ‘Vocal learning in animals and
humans’.

Abstract

Differences in auditory perception between species are influenced by phylogenetic origin and the perceptual challenges imposed by the natural environment, such as detecting prey- or predator-generated sounds and communication signals. Bats are well suited for comparative studies on auditory perception since they predominantly rely on echolocation to perceive the world, while their social calls and most environmental sounds have low frequencies. We tested if hearing sensitivity and stimulus level coding in bats differ between high and low-frequency ranges by measuring auditory brainstem responses (ABRs) of 86 bats belonging to 11 species. In most species, auditory sensitivity was equally good at both high- and low-frequency ranges, while amplitude was more finely coded for higher frequency ranges. Additionally, we conducted a phylogenetic comparative analysis by combining our ABR data with published data on 27 species. Species-specific peaks in hearing sensitivity correlated with peak frequencies of echolocation calls and pup isolation calls, suggesting that changes in hearing sensitivity evolved in response to frequency changes of echolocation and social calls. Overall, our study provides the most comprehensive comparative assessment of bat hearing capacities to date and highlights the evolutionary pressures acting on their sensory perception.

Abstract

Comprising more than 1,400 species, bats possess adaptations unique among mammals including powered flight, unexpected longevity, and extraordinary immunity. Some of the molecular mechanisms underlying these unique adaptations includes DNA repair, metabolism and immunity. However, analyses have been limited to a few divergent lineages, reducing the scope of inferences on gene family evolution across the Order Chiroptera. We conducted an exhaustive comparative genomic study of 37 bat species, one generated in this study, encompassing a large number of lineages, with a particular emphasis on multi-gene family evolution across immune and metabolic genes. In agreement with previous analyses, we found lineage-specific expansions of the APOBEC3 and MHC-I gene families, and loss of the proinflammatory PYHIN gene family. We inferred more than 1,000 gene losses unique to bats, including genes involved in the regulation of inflammasome pathways such as epithelial defense receptors, the natural killer gene complex and the interferon-gamma induced pathway. Gene set enrichment analyses revealed genes lost in bats are involved in defense response against pathogen-associated molecular patterns and damage-associated molecular patterns. Gene family evolution and selection analyses indicate bats have evolved fundamental functional differences compared to other mammals in both innate and adaptive immune system, with the potential to enhance anti-viral immune response while dampening inflammatory signaling. In addition, metabolic genes have experienced repeated expansions related to convergent shifts to plant-based diets. Our analyses support the hypothesis that, in tandem with flight, ancestral bats had evolved a unique set of immune adaptations whose functional implications remain to be explored.

Abstract

High-quality and complete reference genome assemblies are fundamental for the application of genomics to biology, disease, and biodiversity conservation. However, such assemblies are available for only a few non-microbial species1,2,3,4. To address this issue, the international Genome 10K (G10K) consortium5,6 has worked over a five-year period to evaluate and develop cost-effective methods for assembling highly accurate and nearly complete reference genomes. Here we present lessons learned from generating assemblies for 16 species that represent six major vertebrate lineages. We confirm that long-read sequencing technologies are essential for maximizing genome quality, and that unresolved complex repeats and haplotype heterozygosity are major sources of assembly error when not handled correctly. Our assemblies correct substantial errors, add missing sequence in some of the best historical reference genomes, and reveal biological discoveries. These include the identification of many false gene duplications, increases in gene sizes, chromosome rearrangements that are specific to lineages, a repeated independent chromosome breakpoint in bat genomes, and a canonical GC-rich pattern in protein-coding genes and their regulatory regions. Adopting these lessons, we have embarked on the Vertebrate Genomes Project (VGP), an international effort to generate high-quality, complete reference genomes for all of the roughly 70,000 extant vertebrate species and to help to enable a new era of discovery across the life sciences.

Abstract

Background

Heterozygous variants in CNTNAP2 have been implicated in a wide range of neurological phenotypes, including intellectual disability (ID), epilepsy, autistic spectrum disorder (ASD), and impaired language. However, heterozygous variants can also be found in unaffected individuals. Biallelic CNTNAP2 variants are rarer and cause a well-defined genetic syndrome known as CASPR2 deficiency disorder, a condition characterised by ID, early-onset refractory epilepsy, language impairment, and autistic features.
Case-report

A 7-year-old boy presented with hyperkinetic stereotyped movements that started during early infancy and persisted over childhood. Abnormal movements consisted of rhythmic and repetitive shaking of the four limbs, with evident stereotypic features. Additional clinical features included ID, attention deficit-hyperactivity disorder (ADHD), ASD, and speech impairment, consistent with CASPR2 deficiency disorder. Whole-genome array comparative genomic hybridization detected a maternally inherited 0.402 Mb duplication, which involved intron 1, exon 2, and intron 2 of CNTNAP2 (c.97 +?_209-?dup). The affected region in intron 1 contains a binding site for the transcription factor FOXP2, potentially leading to abnormal CNTNAP2 expression regulation. Sanger sequencing of the coding region of CNTNAP2 also identified a paternally-inherited missense variant c.2752C > T, p.(Leu918Phe).
Conclusion

This case expands the molecular and phenotypic spectrum of CASPR2 deficiency disorder, suggesting that Hyperkinetic stereotyped movements may be a rare, yet significant, clinical feature of this complex neurological disorder. Furthermore, the identification of an in-frame, largely non-coding duplication in CNTNAP2 points to a sophisticated underlying molecular mechanism, likely involving impaired FOXP2 binding.

Abstract

How learning affects vocalizations is a key question in the study of animal
communication and human language. Parallel efforts in birds and humans
have taught us much about how vocal learning works on a behavioural
and neurobiological level. Subsequent efforts have revealed a variety of
cases among mammals in which experience also has a major influence on
vocal repertoires. Janik and Slater (Anim. Behav. 60, 1–11. (doi:10.1006/
anbe.2000.1410)) introduced the distinction between vocal usage and pro-
duction learning, providing a general framework to categorize how
different types of learning influence vocalizations. This idea was built on
by Petkov and Jarvis (Front. Evol. Neurosci. 4, 12. (doi:10.3389/fnevo.2012.
00012)) to emphasize a more continuous distribution between limited and
more complex vocal production learners. Yet, with more studies providing
empirical data, the limits of the initial frameworks become apparent.
We build on these frameworks to refine the categorization of vocal learning
in light of advances made since their publication and widespread agreement
that vocal learning is not a binary trait. We propose a novel classification
system, based on the definitions by Janik and Slater, that deconstructs
vocal learning into key dimensions to aid in understanding the mechanisms
involved in this complex behaviour. We consider how vocalizations can
change without learning, and a usage learning framework that considers
context specificity and timing. We identify dimensions of vocal production
learning, including the copying of auditory models (convergence/
divergence on model sounds, accuracy of copying), the degree of change
(type and breadth of learning) and timing (when learning takes place, the
length of time it takes and how long it is retained). We consider grey
areas of classification and current mechanistic understanding of these beha-
viours. Our framework identifies research needs and will help to inform
neurobiological and evolutionary studies endeavouring to uncover the
multi-dimensional nature of vocal learning.
This article is part of the theme issue ‘Vocal learning in animals and
humans’.

Abstract

Exceptionally long-lived species, including many bats, rarely show overt signs of aging, making it difficult to determine why species differ in lifespan. Here, we use DNA methylation (DNAm) profiles from 712 known-age bats, representing 26 species, to identify epigenetic changes associated with age and longevity. We demonstrate that DNAm accurately predicts chronological age. Across species, longevity is negatively associated with the rate of DNAm change at age-associated sites. Furthermore, analysis of several bat genomes reveals that hypermethylated age- and longevity-associated sites are disproportionately located in promoter regions of key transcription factors (TF) and enriched for histone and chromatin features associated with transcriptional regulation. Predicted TF binding site motifs and enrichment analyses indicate that age-related methylation change is influenced by developmental processes, while longevity-related DNAm change is associated with innate immunity or tumorigenesis genes, suggesting that bat longevity results from augmented immune response and cancer suppression.

Abstract

Mutations of the epidermal growth factor receptor (EGFR) gene are found at a relatively high frequency in glioma, with the most common being the de2-7 EGFR (or EGFRvIII). This mutation arises from an in-frame deletion of exons 2-7, which removes 267 amino acids from the extracellular domain of the receptor. Despite being unable to bind ligand, the de2-7 EGFR is constitutively active at a low level. Transfection of human glioma cells with the de2-7 EGFR has little effect in vitro, but when grown as tumor xenografts this mutated receptor imparts a dramatic growth advantage. We mapped the phosphorylation pattern of de2-7 EGFR, both in vivo and in vitro, using a panel of antibodies specific for different phosphorylated tyrosine residues. Phosphorylation of de2-7 EGFR was detected constitutively at all tyrosine sites surveyed in vitro and in vivo, including tyrosine 845, a known target in the wild-type EGFR for src kinase. There was a substantial upregulation of phosphorylation at every yrosine residue of the de2-7 EGFR when cells were grown in vivo compared to the receptor isolated from cells cultured in vitro. Upregulation of phosphorylation at tyrosine 845 could be stimulated in vitro by the addition of specific components of the ECM via an integrindependent mechanism. These observations may partially explain why the growth enhancement mediated by de2-7 EGFR is largely restricted to the in vivo environment