Pregnant mice were used to assess the expression levels of the following genes associated with SARS-CoV-2, inflammation, and other viral diseases:

• ACE2: cellular receptor for the SARS-CoV-2 virus
• TMPRSS2: serine protease involved in cellular entry of the SARS-CoV-2 virus
• St3gal4: related to the influenza virus
• St6gal1: related to the influenza virus
• Ifngr1: related to inflammation
• Tnfrsf1a: related to inflammation

Mice were sacrificed at the following timepoints:

• E12.5: embryonic day 12 (gravid females are sacrificed)
• E14.5: embryonic day 14 (gravid females are sacrificed)
• P1: day pups are born (pups are sacrificed)

Epithelium (Epi) and mesenchyme (Mes) tissue were collected from the soft pallets (SP) and tongues (T) of the different developmental stages. Notably, ACE2 expression was only observed in large quantities in P1 mice, and TMPRSS2 expression increased throughout the developmental process. FPKM: fragments per kilobase million reads