Comparative histological analysis of cerebellum of representative species of elasmobranchii

SUMMARY: In elasmobranch fishes, variations in gross structural organization of cerebellum has been extensively explored. The basic histological features of cerebellum although conserved in the group but the comparative account on subtle cellular variations is largely underestimated. The present study aims to explore the histological and cellular variations in different layers of cerebellar cortex of the representative elasmobranchs' species belonging to different habitat. Our findings showed that the histological architecture of cerebellar granular layer between the examined species varies noticeably. By and large increase cellular density were observed in all the layers of cerebellum in the representative species of shark compared to ray. The findings were then compared and discussed with reference to their habitat and behavior.

En los peces elasmobranquios, las variaciones en la organización estructural general del cerebelo se han explorado ampliamente. Las características histológicas básicas del cerebelo, aunque se conservan en el grupo, pero la descripción comparativa de las variaciones celulares sutiles es limitada. El presente estudio tiene como objetivo explorar las variaciones histológicas y celulares en diferentes capas de la corteza cerebelosa de las especies representativas de elasmobranquios pertenecientes a diferentes hábitats. Nuestros hallazgos mostraron que la arquitectura histológica de la capa granular del cerebelo entre las especies examinadas varía notablemente. Se observó un gran aumento de la densidad celular en todas las capas del cerebelo en las especies representativas de tiburón en comparación con la raya. Luego, los hallazgos se compararon y discutieron con referencia a su hábitat y comportamiento.

Deciphering the genetic architecture and ethnographic distribution of IRD in three ethnic populations by whole genome sequence analysis.

Patients with inherited retinal dystrophies (IRDs) were recruited from two understudied populations: Mexico and Pakistan as well as a third well-studied population of European Americans to define the genetic architecture of IRD by performing whole-genome sequencing (WGS). Whole-genome analysis was performed on 409 individuals from 108 unrelated pedigrees with IRDs. All patients underwent an ophthalmic evaluation to establish the retinal phenotype. Although the 108 pedigrees in this study had previously been examined for mutations in known IRD genes using a wide range of methodologies including targeted gene(s) or mutation(s) screening, linkage analysis and exome sequencing, the gene mutations responsible for IRD in these 108 pedigrees were not determined. WGS was performed on these pedigrees using Illumina X10 at a minimum of 30X depth. The sequence reads were mapped against hg19 followed by variant calling using GATK. The genome variants were annotated using SnpEff, PolyPhen2, and CADD score; the structural variants (SVs) were called using GenomeSTRiP and LUMPY. We identified potential causative sequence alterations in 61 pedigrees (57%), including 39 novel and 54 reported variants in IRD genes. For 57 of these pedigrees the observed genotype was consistent with the initial clinical diagnosis, the remaining 4 had the clinical diagnosis reclassified based on our findings. In seven pedigrees (12%) we observed atypical causal variants, i.e. unexpected genotype(s), including 4 pedigrees with causal variants in more than one IRD gene within all affected family members, one pedigree with intrafamilial genetic heterogeneity (different affected family members carrying causal variants in different IRD genes), one pedigree carrying a dominant causative variant present in pseudo-recessive form due to consanguinity and one pedigree with a de-novo variant in the affected family member. Combined atypical and large structural variants contributed to about 20% of cases. Among the novel mutations, 75% were detected in Mexican and 50% found in European American pedigrees and have not been reported in any other population while only 20% were detected in Pakistani pedigrees and were not previously reported. The remaining novel IRD causative variants were listed in gnomAD but were found to be very rare and population specific. Mutations in known IRD associated genes contributed to pathology in 63% Mexican, 60% Pakistani and 45% European American pedigrees analyzed. Overall, contribution of known IRD gene variants to disease pathology in these three populations was similar to that observed in other populations worldwide. This study revealed a spectrum of mutations contributing to IRD in three populations, identified a large proportion of novel potentially causative variants that are specific to the corresponding population or not reported in gnomAD and shed light on the genetic architecture of IRD in these diverse global populations.

Defining the ends of Parkin exon 4 deletions in two different families with Parkinson's disease.

Autosomal recessive juvenile parkinsonism (AR-JP, PARK2) is characterized by an early onset parkinsonism, often presenting with dystonia as an early feature. Mutations in Parkin are a relatively common cause of AR-JP and are estimated to be present in approximately 30% of familial young onset Parkinson disease (PD) [Abbas et al. (1999); Hum Mol Genet 8:567-574]. These mutations include exon rearrangements (deletions and duplications), point mutations, and small deletions. Similar genomic mutations have been described in unrelated patients, thereby indicating independent mutational events or ancient founder effects. We have identified homozygous deletion mutations of exon 4 in Parkin in two unrelated families, one from Brazil and the other from Turkey [Dogu et al. (2004); Mov Dis 9:812-816; Khan et al., Mov Dis, in press]. We have performed molecular analysis of the deletion breakpoints and this data indicates these mutations originated independently. We present here data demonstrating that the mutation responsible for disease in the Brazilian kindred consists of two separate deletions (1,069 and 1,750 bp) surrounding and including exon 4. The deletion removing parkin exon 4 identified in the Turkish family extended 156,203 bp. In addition to demonstrating that disease in these families is not caused by a single founder mutation, these data show that there is no common fragile site between these mutational events.

Parkin disease in a Brazilian kindred: Manifesting heterozygotes and clinical follow-up over 10 years.

We report on a large Brazilian kindred with young-onset parkinsonism due to either a homozygous or heterozygous mutation in parkin. A total of 6 members were affected: 5 were homozygous and 1 heterozygous for a deletion in exon 4. Two other heterozygotes also had extrapyramidal signs. All affected subjects showed characteristic features of parkin disease with foot dystonia and an excellent response to levodopa complicated by motor fluctuations and dyskinesia within 3 years of therapy. Careful clinical follow-up over 10 years showed the phenotype was similar in all the homozygotes with asymmetrical limb bradykinesia and early walking difficulties. Some acceleration of disability was observed in some of the cases as they entered the third decade of illness, but dementia was absent.