With the recent U.S. Food and Drug Administration (FDA)-approval and rollout of the Pfizer-BioNTech and Moderna COVID-19 vaccines, it is important for radiologists to consider recent COVID-19 vaccination history as a possible differential diagnosis for patients with unilateral axillary adenopathy. Hyperplastic axillary nodes can be seen on sonography after any vaccination but are more common after a vaccine that evokes a strong immune response, such as the COVID-19 vaccine. As the differential of unilateral axillary adenopathy includes breast malignancy, it is crucial to both thoroughly evaluate the breast for primary malignancy and to elicit history of recent vaccination. As COVID-19 vaccines will soon be available to a larger patient population, radiologists should be familiar with the imaging features of COVID-19 vaccine induced hyperplastic adenopathy and its inclusion in a differential for unilateral axillary adenopathy. Short-term follow-up for unilateral axillary adenopathy in the setting of recent COVID-19 vaccination is an appropriate recommendation, in lieu of immediately performing potentially unnecessary and costly axillary lymph node biopsies.

The serotonin transporter (5HTT; chromosomal location 17q12) is an important regulator of serotonergic neurotransmission and is the site of action for a number of antidepressant medications. Sequence variation at a VNTR known as the 5HTTLPR, which is 1.4 kb upstream of the translation start of 5HTT, has been associated in some studies with increased vulnerability to depression, neuroticism, and autism. Support for these clinical observations has included laboratory findings that 5HTTLPR variation is associated with changes in 5HTT gene translation. We re-examined these earlier laboratory findings by directly measuring 5HTT mRNA levels and genotyping four loci spanning the 5HTT gene using RNA and DNA prepared from 85 independent lymphoblast cell lines. Using this data, haplotypes were inferred and the resulting single point and haplotypes data analyzed by univariate and regression analyses. Consistent with the original findings, we found a significant effect of the 5HTTLPR on mRNA production. In contrast to previous reports, the effect on 5HTT mRNA production appeared to be mediated through an additive, not dominant, mechanism. Neither genotype nor haplotype at three other 5HTT loci were associated with alterations in mRNA production, although the small number of samples homozygous for the three most common haplotypes limits these findings. We conclude that further examination of the role of 5HTT sequence variation in regulating 5HTT mRNA production is warranted.

Protein context clearly influences neurotoxicity in polyglutamine diseases, but the contribution of alternative splicing to this phenomenon has rarely been investigated. Ataxin-3, a deubiquitinating enzyme and the disease protein in SCA3, is alternatively spliced to encode either a C-terminal hydrophobic stretch or a third ubiquitin interacting motif (termed 2UIM and 3UIM isoforms, respectively). In light of emerging insights into ataxin-3 function, we examined the significance of this splice variation. We confirmed neural expression of several minor 5′ variants and both of the known 3′ ataxin-3 splice variants. Regardless of polyglutamine expansion, 3UIM ataxin-3 is the predominant isoform in brain. Although 2UIM and 3UIM ataxin-3 display similar in vitro deubiquitinating activity, 2UIM ataxin-3 is more prone to aggregate and more rapidly degraded by the proteasome. Our data demonstrate how alternative splicing of sequences distinct from the trinucleotide repeat can alter properties of the encoded polyglutamine disease protein and thereby perhaps contribute to selective neurotoxicity.

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