SFTPB

Chr 2AR

surfactant protein B

Also known as: PSP-B, SFTB3, SFTP3, SMDP1, SP-B

NCBI Gene: 6439 ENSG00000168878 UniProt: P07988

This gene encodes the pulmonary-associated surfactant protein B (SPB), an amphipathic surfactant protein essential for lung function and homeostasis after birth. Pulmonary surfactant is a surface-active lipoprotein complex composed of 90% lipids and 10% proteins which include plasma proteins and apolipoproteins SPA, SPB, SPC and SPD. The surfactant is secreted by the alveolar cells of the lung and maintains the stability of pulmonary tissue by reducing the surface tension of fluids that coat the lung. The SPB enhances the rate of spreading and increases the stability of surfactant monolayers in vitro. Multiple mutations in this gene have been identified, which cause pulmonary surfactant metabolism dysfunction type 1, also called pulmonary alveolar proteinosis due to surfactant protein B deficiency, and are associated with fatal respiratory distress in the neonatal period. Alternatively spliced transcript variants encoding the same protein have been identified.[provided by RefSeq, Feb 2010]

Primary Disease Associations & Inheritance

Surfactant metabolism dysfunction, pulmonary, 1MIM #265120

UniProtPulmonary surfactant metabolism dysfunction 1

UniProtRespiratory distress syndrome in premature infants

262

ClinVar variants

Pathogenic / LP

0.00

pLI score

Active trials

Clinical Summary— SFTPB

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Gene-Disease Validity (ClinGen)

surfactant metabolism dysfunction, pulmonary, 1 · ARDefinitive

Definitive — sufficient evidence for diagnostic panels

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Population Constraint (gnomAD)

Low constraint (pLI 0.00) — loss-of-function variants are relatively tolerated in the population.

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ClinVar Variants

34 Pathogenic / Likely Pathogenic· 105 VUS of 262 total submissions

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Clinical Trials

2 active or recruiting trials — potential therapeutic options may be available

Population Genetics & Constraint

gnomAD v4 — loss-of-function & missense intolerance

gnomAD

Tolerant — LoF & missense variants common in population

LoF Constraint?LOEUF (Loss-of-function Observed/Expected Upper bound Fraction) is the upper bound of the 90% CI for LoF OE — the preferred gnomAD v4 metric. Lower = more intolerant to LoF. LOEUF < 0.35 = highly constrained.

0.72LOEUF

pLI 0.000

Z-score 2.59

OE 0.42 (0.26–0.72)

Tolerant

Typical tolerance to LoF variation

Missense Constraint?Missense Z-score: standard deviations fewer missense variants observed vs. expected. Z > 3.09 (p < 0.001) = gene does not tolerate missense variation. OE missense < 0.6 is also considered constrained.

0.60Z-score

OE missense 0.89 (0.79–1.00)

202 obs / 227.3 exp

Tolerant

Mild missense constraint

Observed / Expected Ratios?Shaded band = 90% confidence interval. Vertical tick = point estimate. Grey threshold line = gnomAD constraint cutoff for that variant class.

LoF OE?Ratio of observed to expected LoF variants. Upper CI bound (LOEUF) ≤ 0.35 = strong LoF constraint signal.0.42 (0.26–0.72)

0≤0.351.4

Missense OE?Ratio of observed to expected missense variants. OE ≤ 0.6 = fewer missense variants than expected by chance.0.89 (0.79–1.00)

0≤0.61.4

Synonymous OE?Control metric — synonymous variants are largely neutral and expected near OE = 1.0. Significant deviation may indicate annotation issues.0.94

0≤1.21.6

LoF obs/exp: 10 / 23.6Missense obs/exp: 202 / 227.3Syn Z: 0.49